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| Question | Answer |
|---|---|
| List 3 types of forensic techniques? | 1. Fingerprinting 2. Dental Records 3. DNA Profiling |
| What are fingerprints and why are they used? | They are small ridges caused by folds in the epidermis of the skin. Sweat and oil secretions leave impressions of fingerprints. They are individual and unique. |
| Name 4 types of fingerprint patterns? | 1. Arch 2. Tented Arch 3. Whorl 4. Loop |
| How can fresh fingerprints be made visible? | 1. Fine aluminium,iron or carbon powders that stick to print. 2. Using superglue 3. Using ninhydrin reacts with AA in sweat to produce purple coloured fingerprints. 4. Vacuum metal deposition 5. Megnets and Iron flakes |
| How are Dental records used? | Teeth and fillings decay slower and are res. to fire. F. dentist makes accurate chart of the teeth and then is compared with dental records. |
| What is DNA Profiling? | A technique that allows us to identify biological material with a high degree of confidence. |
| How many genes does the human genome contain? | 23000 genes. A large amount of DNA does not code for proteins. |
| What are introns and exons? | Non-coding blocks are introns and the coding blocks are exons. |
| What are STR's?(Short tandem sequences) | Short DNA sequences of repeated bases which are found in introns. The same STR's occur at the same place on both chromosomes of a homologous pair. The no. of time they are repeated are different. The number of repeats at a locus varies between each indv. |
| Why is DNA unique? | Variety found in the sections of DNA which are not used to code proteins.Scientists look at STR repeats at many loci to build up unique pattern for indv. |
| How is a DNA profile made? | 1.Gain tissue sample and extract DNA. 2.Cut DNA to create fragments of different lengths. 3.Fragments are separated and visualised. 4. Then compared to ref profile. |
| How do you obtain DNA? | 1. Cheek swab at police station or medical clinic 2. White blood cells in a blood smear at scene of crime 3. Bone marrow from skeleton 4. Sperm from sex. assault |
| How is DNA extracted? | Tissue sample phys. broken down in b. sol(salt & detergent)disrupt cell membrane.Particles separated by centrifuging/filtering. Protease enzymes are incubated + suspension to remove proteins & cold ethanol added to precipitate DNA. Wash DNA with b.sol. |
| How do you create the fragments? | Treat DNA sample with r.enzymes (r.endonucleases). Found in bacteria to cut v.DNA. Will only cut spec. base seq. If either side of STR; fragment will stay intact but will cut rest of genome. |
| Where does EcoRI come from? | Escherichia cole |
| How do Bacteria protect their own sequences? | Changing the bases in the sequences that are targeted by their own restriction enzymes.What |
| What do the r.enzymes do? | Cut DNA sample into fragments only where restriction seq. occurs. If same r. enzyme is used to cut identical DNA, identical STR fragments are produced. |
| What does PCR allow? | Small samples of DNA to be amplified so they can be used for DNA profiling, where DNA is copied numerous times using DNA primers. |
| What are DNA primers? | They are short DNA seq. comp. to the DNA adjacent to the STR. They are marked with fluorescent tags. |
| What is added to the sample? | DNA Polymerase, DNA primers and nucleotides. |
| What happens in the three temp changes? | 1. Separates double strand DNA. 2. Optimises prime binding to target DNA seq.in sample.Polymerase attaches & replication occurs. 3. Opt. temp for heat- stable DNA polymerase. Huge no's of DNA fragments being produced. |
| What is the aim of PCR? | To produce huge nos. of targeted DNA fragements. |
| How is the gender determined? | By adding an extra primer. |
| How do you separate the fragments? | Gel Electrophoresis |
| What is the process of separating DNA? | 1. DNA is placed on gel agarose or polyacrylamide; this provides a stable medium through for fragments to move. 2.Gel is submerged in b.solution and connected to electrodes that produce pd. across gel. 3.Neg. charged fragments migrate through gel |
| What fragments travel faster? | Smaller fragments with small no. of repeat seq. |
| What determines the fragments? | Charge and size |
| What is a DNA ladder? | A ref. sample with fragments of known length added to the gel. |
| What happens after electrophoresis? | Gel is fragile and DNA fragments are double stranded. |
| What is S.Blotting? | Transfer fragments to a more resilient nylon or nitrocellulose membrane. The membrane is placed directly onto the gel and a wad of dry absorbent paper placed on top. This acts as a wick to draw b.solution up gel, carrying fragments onto membrane. |
| What happens during this? | Fragments maintain positions rel. to each other and denatured into single strands; exposing base sequences. |
| How are the fragments visualised? | Membrane is incubated + excess labelled DNA probe;short section of DNA with base seq comp. to target DNA seq. needing to be located. After allowing time for probe to bind to comp. seq. any unbound probe is washed away. |
| How are the fragments visualised? | With radioactive probe, membrane is dried and placed near X-ray film. The film blackens where probe has bound with DNA to form double strand fragments. If probe is fluorescent,pos.can be visualised under UV. |
| When is a band formed? | Single band can be formed on a profile where a persons maternal & paternal chromosomes have the same no.of repeats at a particular locus. Two bands occur on profile of 2 chromosomes have different no. of repeats at a locus creating banding pattern? |
| How may DNA profile not be unique although STR seq. are? | If only a few probes are used and analyses a few rep. seq |
| How are the fluorescent band detected? | They are caused by fluorescent tags on the DNA primers attached to the target DNA. This is detected by a laser scanner or camera. |
| What does the graph DNA profile correspond? | Pos. of peak on x-axis corresponds to size of DNA fragment and height indicates amount of DNA. Colour of peak rel. to the fluorescent-coloured tag attached to primer. |
| What is the different between graphs? | Graph is interpreted to give series of no's corresponding to no. of repeats in each fragment. |
| Why are there sometimes two different figures for some of the satellites? | No. of repeated seq. in different one each chromosome in a homologous pair. |
| What are the uses of genetic profiling? | Identification purposes, paternity disputes,Identifying stolen animals and looking into variation and evolutionary relationships |
| What are the uses in genetic profiling? | confirming pedigree of dom. animals,purity of food samples and det. father of child. |
| What are the three ways to est. time of death? | 1.Temp of body 2.Rigor Mortis 3.State of decomposition |
| What happens to human body temp when a person dies? | Body starts to cool due to absence of heat-producing chem reactions. Useful to est. time of death during first 24 hrs post-mortem. |
| How can core temp be measured? | Using a long thermometer as ordinary one is too short and has a small temp range; through the rectum or abdominal stab. OR using an electronic temp. probe. |
| What curve does the cooling of a body produce? | A sigmoid curve. |
| What may elevate of depress one's body temp? | Hypothermia or fever. |
| What factors affect post-mortem cooling? | Body size Body pos. Clothing Air movement Humidity Temp of surroundings |
| What happens during rigor mortis? | Muscles relax and stiffen. Joints become fixed dep. on body pos during 6-9 hrs. Stiffening of muscles is r.mortis. |
| What is the following seq. that takes place? | 1.M.cells oxy starved,oxy-dep reactions stop 2.Resp.in cells anaerobic,prod.l.acid 3.cell pH drops,inhib.enzymes and AR 4.ATP for muscle cont x produced.Bonds between muscle prot.fixed 5.Proteins X move one another to short. muscle; fixing muscle & jo |
| What muscles stiffen before? | Smaller muscles. |
| Why may r. mortis set more quickly? | Env. temp is high or physically active. |
| What happens first after death? | Tissues break down due to enzymes from d.tract & lysosomes. Bacteria from gut and gas.exchange rapidly invade tissues after death releasing enzymes that res. in decomposition. Loss of oxygen in tissues fav. growth of anaerobic bacteria. |
| What are the signs of decomposition? | Greenish discol. of skin of l.abdomen. Due to sulphaemoglobin in blood. This will spread across body and darken to reddish green then purple-black and gas formation |
| How does Ammonia,hydrogen sulfide, methane, carbon dioxide, form in intestines and tissues? | Due to the action of bacteria causing body to deflate. Causing body to smell and become bloated. |
| What does putrefaction result in? | Liquefication of body tissue. |
| How long does discoloration of abdominal wall take? | 36-72 hrs after death. |
| What det. rate of decomp? | Temp. Gas formation after a week or 3 days if above 26 degrees. |
| What happens in low temp? | Decomp. is slower .R. mortis dev. slowly. Lower met. rate and therefore takes longer for oxygen to run out and persists longer. |
| What happens in high temp? | Speeds up decomp. R. mortis dev. rapidly. High met.rate therefore oxygen runs out quicker and lasts for slower time. Lysosomal enzymes work faster. |
| What happens if there is intense heat? | Denatures enzymes. |
| What may allow entry of bacteria to aid decomposition and increase rate? | Injuries to the body. |
| What affects of demposition? | Env temp Body clothed/buries |
| How to presence of insects help? | To make est. of how much time has elapsed after death. |
| What is the process of this? | 1. They take record info of location an cond. of body 2.Samples of insects found on/near body 3.Temp of ground,air,body and maggot mass for rate of maggot development to be determined. |
| How can temp history be det? | Local meteorological records or weather stations nearby. |
| What will happen to the maggots? | Some will be killed or some taken alive and fed on meat to further development. |
| Why is this useful? | To identify species and to establish when they pupate. |
| Why can insects be used? | As many types of flies will lay their eggs in a dead body so therefore acts as a source of food for the larvae. Eggs can be laid on skin, bod openings; ears nose mouth or wounds. Can give ind. of when eggs were laid and time of death. |
| How may you est. the age of C. vicina? | On graph; using the temp of place where maggot was found and length, maggot age can be read. |
| When can the graph only be used? | When the temp. of the body has remained constant. |
| What would happen if stage of development is unclear? | It will be allowed to mature to give date of pupation. Normal length of time for an egg to dev. and pupate is subtracted from date of pupation; to work out when eggs were laid. |
| Why may it give underestimate of death? | As we don't know how long it took flies to find the body. |
| What may affect results? | Toxins and cocaine/ecstasy. |
| How are maggots useful in medicine? | They clean wound and ea dead and dying flesh and leave healthy tissue. |
| What happens in succession of corpses? | Organisms feeding off the body changes the body making it more attractive to another group which changes the body for the next group. Increases species, biodiversit, biomass. |
| What det. the community of insects? | The cond. and how this changes with each stage on succession. |
| What will influence type and no. of species present? | Season, weather cond, size and location of body. |
| Where may C.vicina be found? | Urban situations. |
| Where may C.vomitoria be found? | Rural locations; rarely indoors. |
| Where do Bluebottles lay their eggs? | Shaded situations. |
| Where do greenbottle lay their eggs? | Sunny spots. |
| What organisms appear in first wave when body is fresh? | Calliphora.vicina, Calliphora.vomitoria, (Bluebottles)Lucilia sericata, Musca domestica, Musca Autumnalis. |
| What organisms appear in second wave when body is bloated by gases? | Sarcophaga species. |
| What organisms appear in third wave when body is affected by active decomp(fatty acids turned to waxy sub) | Dermestes, Aglosa |
| What organisms appear in fourth wave when body is affected by active decomp (fermentation)? | Piophilia, Fannia canicularis. |
| What does the length of each stage in succession depend on? | Cond. of body which depends on env cond. |
| What is the different between this and plant succession? | Early species are not replaced as cond change; most of the insects remain on body till adv. stages of decay. |
| How can insects det. if body has been moved? | As species of insect may be found that would not naturally occur. |
| What other decomposers are invd? | Bacteria from gut invades tissues after death. Other bacteria & fungi from surroundings colonise corpe; contributing to decay and changing cond. on decomposing body. |
| What are bacteria in stages? | Bacillus, Staphylococcus, Candida and Streptolococcus. Followed by Salmonella, Cytophaga and Agrobacterium. |
| Why is a corpse a great source of energy? | Org Carbs, proteins, fats and nucleic acids are used a food source, with energy being released through aerobic and anaerobic resp. Enables bacteria and fungi to grow and multiply rapidly. |
| Why is Decomposition important? | CO2 is released into atmos by decomposers. This recyles carbon back into a form for photosynthesis by plants to synthesise more organic molecules. Major process of sustaining carbon cycle and cont. of life on earth. |
| What are the 5 ways to indicate time of death? | 1.Body temp. 2.Deg. of muscle cont. 3.Ext. of decomp 4.For. Entomology 5.Stage of Succ. |
| Why may a post-mortem be carried out? | If the death is unexpected/sudden or death is unknown. |
| What examinations are then taken? | Ext.Int;Incision made down front of body & organs taken out for det.examination. State of organs allows conc.about health of person. E.g. heart/atherosclerosis or heart attack, cirrhosis/death of liver cells & form. fib.tissue/inadq diet,exc alc or inf. |
| What is bacteria responsible for Tuberculosis? | Mycobacterium tuberculosis |
| What virus is responsible for AIDS? | HIV (Human Immunodeficiency Virus) |
| What type of cells are bacteria? | Prokaryotic cells. |
| What are the main features of bacteria? | - X nucleus - Lack membrane bound organelles - X produce spindle for cell division - 0.5 -5 um - Reproduce Asexually by B.fission - After rep. divide into 2 cells |
| What are the components of bacteria? | Cell Wall Capsule Flagellum Cell Surface Membrane Ribosomes Pilus Main Circular DNA Mesosome Plasmids |
| What is a virus? | Small organic particles with a structure that is quite different from bacteria and much simpler. They consist of a strand of nucleic acid (RNA or DNA ) enclosed within protein coat.V.DNA can be single or double stranded. |
| Where might a viruses outer envelope be taken from? | Host cell's surface membrane; envelope therefore contains lipids and proteins. V. envelopes also have glycoproteinsfrom virus itself. These are antigens, molecules recognised by host's immune system as not being its own self. |
| How may the envelope help? | Helps the virus to attach to the cell and penetrate the surface membrane. |
| Why do Viruses have to enter the cells of organisms to use the host's cells met. system to make more viruses? | Lack int.structures for growth & rep. |
| What is the process of Viruses using the host? | 1.Viruses attach to host cell 2.Inserts nucleic acid 3.Viral nucleic acids replicate 4.Viral proteins coats synthesised 5.New virus prticles formed 6.Virus particles released due to cell lysis. |
| What are Bacteria and Viruses known as ? | Pathogens |
| What diseases caused by Bacteria? | Salmonella,Food poisoning, gonorrhoea and cholera. |
| What diseases caused by Viruses? | Flue, Measles, Chicken pox and cold sores. |
| How is M.tuberculosis carried? | Droplets of mucus and saliva released into the air when an infected person talks,coughs or sneezes.Then others inhale the dropelets. This is knows as droplet infection. |
| What factors increase a persons risk of developing the disease? | Poor health, poor diet and overcrowded living cond, close contact with inf. person. Alsi the bacterium is a tough bacterium and can survive as dust from dried droplets for sev. weeks; making bedclothes and room of TB patient pot. infectious. |
| How is HIV transmitted? | Body fluids; blood,vag.secretions,breast milk and semen. NOT SEMEN, SALIVA OR URINE. |
| What is the difference between the M.tuberculosis and HIV? | HIV unlike M.tuberculosis is not a very tough virus and therefore cannot survive outside the body for any sig. time. |
| How can infection occur? | Through unprotected sex with someone who is infected or if blood from person enters your bloodstream. |
| How can body fluids be transferred directly to host? | 1.Sharing needles;illegally for drugs/legally. 2.Unprotected sex,virus enters bloodstream through breaks in skin/lesion caused by infections(STI's). Condom can prev.transmission. Also through oral sex. |
| How can body fluids be transferred directly to host? | 3.D.blood-blood transfer/cuts & grazes. Police,paramedics & med.staff are at risk & precautions are taken. 4.Mat. transmission from mother to child/breast milk. Risk virus being passed occurs last few wks around birth.anti-HIV drugs and Caesarian sectio |
| What is the problem with prev. HIV being transmitted using C-section and anti HIV drugs? | It is only available in countries with adv. med care. |
| What is an immune response? | When the Immune system prev. invading pathogens. |
| What is a non-spec response? | Helps to destroy any invading pathogens. |
| What is a spec response? | Directed at spec. pathogen. |
| What is an antigen? | A molecule the body recognises as not being of its own self. |
| What is lysozyme action? | An enzyme found in tears,sweat,saliva and nose destroys bacteria by breaking down bacterial cell walls.Catalysing insertion of water molecule at certain pos. |
| What is Inflammation? | 1.Injury,cut/graze enables microbes/foreign material enter body. 2.IR/destroy invading microbes. 3.Damaged WBC and mast cells found in c.tissue below skin around b.vessels release histamine. |
| What is Inflammation?(2) | 4.Cause art. dilate,inc.blood flow in cap at inf. site. 5.Histamines increase perm. of cap.;cells in the cap. walls separate slightly,vessels leak. 6. Plasma fluid,WBC & AB leak from blood into tissue causing oedema. Inf. microbes can be attacked by WC |
| What is the function of Inflammation? | 1. To destroy cause of infection and remove it and its products from the body. 2.To limit spread of infection. |
| Why do people take Anti-Histamine tablets? | Antihistamines bind to histamine receptors and block the binding of histamines. |
| What is the Phagocytosis? | WBC engulf,digest and destroy bacteria and foreign material. These phagocytes incl. neutrophils and monocytes which become macrophages. |
| What are neutrophils? 70% | They are white cells that leave blood cap. by squeezing between the cells of cap.walls. They also ingest and destroy bacteria. 80 mill are produced every min. and they last a few days |
| What are lymphocytes? 24 % | They are white cells, consisting of 2 types; B and T cells. They are invd. in IR incl. AB production and immunity. Some last a few days, others last days. |
| What are monocytes? 4 % | White cells that circulate blood for a day or two before they move into the tissue by squeezing between the cells of cap.walls. They become macrophages & engulf bacteria, FM and cell debris.Numerous in lungs, liver, kidneys, spleen and lymph nodes. |
| What do the other 2% of WBC do? | They produce the chem. histamine invd. in IR. |
| What are the features of RBC? | They have no nucleus, they contain haemoglobin,transport oxygen and some CO2. |
| What are the features of WBC? | They contain a nucleus. |
| What are the features of Platelets? | Cell fragments invd. in blood clotting. |
| What happens at the infected site? | Chem. are released by bacteria & cells damaged at site of infection attract phagocytic WC. Neutrophils are first to arrive,engulf bacteria(5-20)before they come inactive & die. Then macrophages destroy around 100 bacteria. |
| What happens at the infected site? [2] | They will ingest debris from damaged cells & FM e.g. particles of carbon and dust in lungs. Ing. material is enc. within vacuole. Lysosomes cont dig. enzymes fuse with vacuole,enzymes are released & they destroy bacteria or FM. |
| What happens at the infected site? [3] | Large no of phagocytic cells that collect at site of infection can engulf huge no of bacteria.After few days,full of dead cells,mainly neutrophils forming thick fluid,pus. May break through skin but gradually gets broken down and absorbed to surr.tissue. |
| What actions take place to prev the spread of infection? | Live bacteria get carried by blood or lymph, the spread of these bacteria is hindered by action of macrophages in the lymph nodes,spleen and liver. |
| What happens if the system fails? | Infections can take place known as septic shock or blood poisoning. |
| What is the process for this? | 1.T.fluid drains into lymphatic vess. 2.Fluid called lymph,flows along l.vess.Pass through l. nodes,returns to blood via lymphatic/thoracic ducts. 3.Passes through the l.nodes,pathogens pres.activate lymphocytes & macrophages which can destroy microbes. |
| What is Interferon? | A protein produced where is diffused to the surrounding cells where it prevents viruses from multiplying. It inhibits protein synthesis, which limits the formation of new virus particles. |
| What is the difference the other methods and this method? | It provides non-specific defence against viruses. |
| What is the aim of Interferon? | It inhibits viral. protein synthesis and therefore limits formation of new virus particles. |
| Where is it secreted from? | Infected cells or when lysis takes place to release virus. |
| What is the significance of Interferon? | 1. Reacts v. quickly 2. Limits the infection until slower acting spec. immune response takes over. |
| What are Lymphocytes? | White blood cells that help to defend the body against spec. diseases.There are two types B and T cells.Response by lymphocytes is called Spec. Immune Response. |
| Where are res. supplies of lymphocytes held? | Strategically-pos lymphoid tissue. |
| What do B and T cells do? | Respond to antigens such as the ones on the surface of bacteria or viruses.Most antigens are protein molecules ; large size and characteristic molecular shape allow lymphocytes to identify which ones are 'foreign'(non-self) |
| What is the name given to this type of response? | Spec. Immune Response |
| What do B cells do in response to antigens? | They secrete antibodies. Each B cell produces 1 type of antibody; which binds to only one specific antigen. A microbe usually has different types of antigens on surface; therefore each antigen will bind and act. different b cells. |
| What are antibodies and what do they do? | They are secreted by B cells and are special protein molecules known as immunoglobulins. They bind to the antigens on the cell surface membrane. They act as labels allowing phagocytes to recognise and destroy cell. |
| Where are B cells produced and when? | In early human embryo dev. in the bone marrow. |
| What happens to these B cells? | They divide to produce clone of cells prov. the baby with an immune system that can respond to different antigens that may invade after birth. |
| What do B cells have on their surface? | Receptors; incl. transmembrane versions of the antibody molecules they produce. |
| What are the features of an antibody? | 1. Disulphide bonds hold the polypeptide chains together. 2.AA seq. and shape of the binding site is different in each type of antibody. |
| What is the process where antibodies attach to the antigens? | 1. Antibodies bind to antigens on the surface of bacteria and label them 2. Antibody binds to the antibody receptor 3. Macrophage engulfs antibodies and bacterium 4.Lysosomes fuse with vacuole, releasing d. enzymes |
| Where are T cells produced? | In the bone marrow and mature in the thymus gland. |
| What do T cells have on their surface? | One spec. type of antigen receptor on their surface. This only binds to an antigen with the comp. shape. |
| What is the process of T cells moving from bone to blood? | 1.Imm. T cells prod. by div. of stem cells in BM 2.Imm. T cells move to thymus by blood 3.T cells mature in thymus 4.Mature T cells leave thymus in blood,move to l.nodes & spleen 5.As l.fluid passes through l.node, T cells are activated by pathogens p |
| What two types of T cells are there? | 1. T helper cells 2. T killer cells |
| What are T helper cells? | When act.they stimulate the B cells, to divide and become cells capable of producing antibodies. They also enhance activity of phagocytes. |
| What are T killer cells? | They destroy any cells with antigens on the surface membrane that are recognised as foreign or 'non-self'. This incl. body cells infected with pathogens. It also invades tissues received by a transplant from another person. |
| What is the process of activating T cells? | 1.Bacterium is engulfed by macrophage 2.Protein fragments become attached to proteins in cell 3.Displayed as antigens on cell surface membrane 4.Antigens are pres. on surface of macrophages & becomes an APC 5.T helper cell with comp. shaped receptors, |
| What is the process of activating T cells?[2] | receptors on its surface binds to antigen on the surface of the APC. 6.Once act. each T helper cell divides to produce a clone of active T helper cells and a clone of T memory cells. |
| Why are the antigens pres. on the surface of macrophages? | To alert the Immune System to the pres. of foreign antigens in the body. |
| What is the use of T memory cells? | It remains for months or years in the body therefore if an indv. is exposed to the same antigen in the future their immune system can respond more quickly. |
| What is the process of Clonal selection? | 1.Antigen from bacterium binds to B cell with comp.receptor. 2.B cell becomes APC 3.Act.T helper cell with comp.receptor binds to APC & produces cytokines that stimulate B cell 4.B cell divides to give, B memory and B effector cells. |
| What is the process of Clonal selection?[2] | 5.B effector cells differentiate into plasma cells 6. Plasma cells secrete antibodies which bind to antigens, identifying them for easier destruction. |
| What happens to B cells under the infl of cytokines? | They produce B effector cells which differentiate to produce plasma cells which release antibodies in blood and lymph and are short lived, lasting only a few days. |
| What happens to B cells under the infl of cytokines? [2] | They produce B memory cells, these cells are longer-lived. |
| How long does a primary immune response take? | 10-17 days. Person is likely to suffer symptoms |
| What is the role of T killer cells? | 1.Bacterium/virus infects body cell,fragment of antigen is pres. on c.s.m;T killer cells with comp.receptors bind to antigen pres.on body cell. 2.T killer cells divide,form active clone which is stimulated by cytokines from T helper cells |
| What is the role of T killer cells?[2] | 3.T killer cells release enzymes,create pores in membrane of infected cell. Allows ions & water to flow into infected cell,swells & burst (lysis) 4. Pathogens are released and labelled by antibodies of B cells as targets for destruction by macrophages |
| Why does the secondary immune response respond much faster? | As it inv.memory cells and only takes 2-7 days.As B memory cells produced in primary response can differentiate immediately to produce plasma cells and release antibodies. |
| What is the difference between primary and secondary immune response? | Quicker and longer response. Greater prod. of antibodies. The invading virus/bacteria are often destroyed so rapidly that the person is unaware of any symptoms. Therefore is immune to disease. |
| How does it prevent an attack from its own immune system? | Membrane protein on surface of cell act as bar codes and mark the body cell as 'self' to distinguish between our cells and foreign invaders. |
| Why it that the combination of proteins found on the cell surface can not be found on cells of anyone else? | As there are hundreds of alleles for the proteins and therefore the combination of protein on our cell surfaces is unique to each indv. |
| What happens when B and T cells mature in the BM and Thymus? | Any lymphocytes for self membrane proteins are destroyed by apoptosis and therefore lymphocytes with receptors for foreign 'non-self' antigens remain. |
| Why may the body attack itself? | Part. cells may alter so they appear foreign and get destroyed by immune system. 1. Auto-destruction of insulin-secreting cells in the pancreas, leading to insulin-dep. diabetes 2. Rheumatoid arthritis 3.MS |
| What bacterium causes Tuberculosis? | Mycobacterium tuberculosis |
| What factors improved the no of people living with TB | 1.Improved hosuing and living cond. 2.Dev. of antibiotics |
| When may infection of Tb actually occur? | When M.tuberculosis bacteria are inhaled and lodge in the lungs.This is where they multiply. |
| How long may the first phase(primary infection) last? | Several months and they may have no symptoms. |
| What does the M.tuberculosis cause? | An inflammatory response from the host's immune system. In an indv with a healthy immune system, macrophages engulf the bacteria. |
| What is the name of the mass of tissue produced in response to the infection? | A granuloma. In TB these tissue masses are anaerobic and have dead bacteria and macrophages in the middle.They are called tubercules. |
| What happens after 3-8 wks? | The infection is controlled and the infected region of the lung heals. |
| Why is it that normally a macrophage can engulf the bacteria and destroy it but in Tb this is not possible? | This is because the bacteria have very thick waxy cell walls, making it difficult to break down. |
| What is the outcome of this? | It can lie dormant for yrs and if the immune system is weakened it can become active again. |
| What else can Tb bacteria do? | They can target the cells of the immune system and therefore suppress the no. of T cells. |
| What is the outcome of this? | Decrease in antibody production. Attack by killer T cells. |
| When does the Second phase (Active TB take place? | If the patient's immune system cannot contain the disease when it arrives in the lungs. |
| Why may this be? | If the no. of bacteria is too great or an old infection may break out if the immune system is no longer working properly. |
| Why may the activity of the immune system be reduced? | 1. Old age/v.young it is less able to respond quickly to pathogens 2. Malnutrition 3. Poor living cond. 4. AIDS |
| Why may AIDS affect the activity of the immune system? | As HIV the virus that causes AIDS, directly targets white blood cells and reduces a patient's ability to fight any infection. |
| Where does Active Tb(Resp. Pulmonary TB) mainly effect? | The lungs. |
| What happens in the lungs? | Bacteria multiply rapidly & destroy lung tissue, creating holes or cavities. This damage will eventually kill the sufferer if they are not treated with an appropriate antibiotic. |
| What are the symptoms of active TB? | 1.Coughing; may cough up blood 2.Shortness of breath 3.Loss of appetite and weight loss 4.Fever and extreme fatigue |
| Why does a person infected with TB exp. fever and night sweats? | Part of the inflammatory response,fever-causing substances are released from neutrophils & macrophages. These chem. affect the hypothalamus and alter the set point for the core temp to a higher temp. The effectors act to warm the body to a new set point. |
| What would the high temp be raised to? | 40.5 C |
| How does the raised temp. affect the immune function? | It enhances immune function and phagocytosis. |
| How does the raised temp. affect the bacteria? | Also it allows bacteria and viruses to reproduce more slowly at higher temp. TB is temp-sens and therefore will stop reproducing at temp. above 42 C. |
| Why is it that temp. over 40 C may be classified as dangerous? | Human enzymes are denatured. |
| Where are other places TB can affect? | Bones, lymph, nodes and central nervous system. |
| What is the main symptom of Glandular TB? | Enlarged lymph glands usually in the neck or armpits. |
| What can be used to see whether the lymph glands in the chest are affected? | X-ray. |
| What race is like to get TB? | Caucasians- Pulm. TB Asians - Gland. TB |
| What is the process to see if someone has TB? | 1.History 2.Symptoms 3.Tests |
| How is a skin and blood test carried out? | 1.Small amount of tuberculin is injected under skin of forearm 2.Pos. result shows an inflamed area of skin around the site of test injection 3. Antibodies in blood cause this inflammation,ind. TB antigens are present. |
| What other results may come up? | 1. Neg. result if the person has latent TB i.e. disease is not active. 2.False pos. result if person had a BCG anti-TB vaccination |
| How can we overcome these problems? | Using blood tests that analyse blo0od samples for T cells spec. to antigens only occuring on M.tuberculosis. |
| What is tuberculin? | Extracts from sev. species of Mycobacteria and is usually composed of a mix. of purified protein |
| How can we confirm a pos. skin test? | To confirm a pos. skin test; sample of sputum coughed up by patient is taken and cultured to see what bacteria is present. |
| How can different bacteria be identified? | By staining techniques as a variety of stains as only some types of bacteria take up part. stains;dep on makeup of their cell wall. |
| Why are chest rays usually taken? | To discover the ext. of the damage and disease in the lungs |
| What types of treatment would be advised? | Combo of antibioticsand improved lifestyle. |
| What would happen if the TB sufferer is contagious? | Recent contct e.g friends and family should be tested; to check whether they have been infected. |
| What are the reasons for lower estimates of AIDS? | Improved mthodology, better HIV surveillances by countries anc changes in key epidemiological assumptions to calc estimates. |
| Why is the amount of est. AIDS decreasing? | 1. HIV prev. programmes 2. Access to drugs |
| What is AIDS and what is it caused by? | Acquired Immune Deficiency Syndrome, caused by an infection with the human immunodefiency virus, HIV. |
| What are the features of the a HIV virus? | (Glycoprotein Lipid bilayer) mRNA(2 copies) Capsid made up of proetins units Layer of viral protein Viral proteins e.g. rev. transciptase and integrase |
| Where is the lipid envelope formed from? | The host cell membrane as the new virus particles emerge from the cell cytoplasm. Sticking through the envelope are v. glycoprotein (gp) molecules. |
| What does HIV do? | Invades T helper cells within the immune system.Part. glycoprotein molecules called gp120 & located on virus surface,bind to the CD4 receptors on surface of the T helper cells. |
| What does HIV do?[2] | Then combine with second receptor which allows envelope surrounding virus to fuse with the T helper cell membrane, enabling viral RNA and enzymes to enter the cell. Macrophages also have CD4 receptors, so the virus can also infect them. |
| What happens once inside the host T helper cell? | Virus needs to make the host cell replicate new viral components.HIV nuclear material is in the form of RNA not DNA. |
| What is the first step in the T helper cell? | 1. Reverse normal transcription and manufacture DNA from RNA template. To do this, virus uses an enzyme called rev. transciptase. |
| What is a retrovirus? | Viruses that contain RNA and use rev. transcriptase(to manufacture DNA from RNA). |
| What happens once the HIV DNA strand is produced | It is integrated into the host's cell DNA by another HIV enzyme, integrase. Once HIV genome is integrated into the host cell's genome it can be transcribed and translated to produce new viral proteins. |
| What is the process of rev.transcriptase? | 1.Rev.transcriptase makes a DNA copy of the RNA 2. DNA is copied to make a double strand that can be inserted into the human genome. |
| What is the process of Protein synthesis (transcription)? | 1.Enzyme,RNA polymerase attaches to DNA 2.H bonds between paired bases break & DNA unwinds 3.RNA nucleotides with bases comp. to those on the template strand of the DNA pair up & bond to form mRNA molecule 3. mRNA leaves nucleus via pore in nuclear e |
| What happens to the mRNA passes out of the nucleus? | It attaches to the ribosome. which is usually attached to the endoplasmic reticulum. |
| What is the process of Protein synthesis (translation)? | 1.mRNA attaches to surface of ribosome 2.tRNA is triplet base seq;anticodon which is comp.to mRNA codon for amino acid. 3.Within cytoplasm free AA attach to tRNA molecule,each AA has its own spec. tRNA that carries it to ribosome 4.1st codon;start cod |
| What is the process of Protein synthesis (translation)?[2] | 5.tRNA + comp.anticodon,H bonds to codon 6.Codon attracts tRNA AA complex + the comp.anti-codon & binds to it 7.Ribosome holds mRNA,tRNA,AA & enzyme while pep bond forms between AA Pep bond is cond. reaction between amine of AA & CA to form dipep. |
| What is the process of Protein synthesis (translation)?[3] | 8.Once pep. bond has formed , ribosome moves along mRNA to reveal new codon at binding site 9.First tRNA returns to cytoplasm 10. Whole process is repeated until the ribosomes reach stop signal |
| Why is the triplet code important? | With 20 amino acids and start/stop signals to code and only four bases; using three bases gives 64 codons which is more than enough. |
| Why is non-overlapping important? | As each set of three bases forms one triplet, the triplets don't overlap so no base from 1 triplet , avoiding confusion about which amino acid is being coded for. |
| Why is degenerate important? | As some amino acids have more than one codon. As long as the codon starts with CC the Amino acid proline will be put into the polypeptide. The code is said to be degenerate; this offers protection against mutation. |
| What happens between transcription and translation? | mRNA splicing, where non-coding introns will be removed, leaving coding exons. Therefore this means sev. proteins canbe formed from one length of mRNA if spliced this way. |
| What are the adv. of mRNA splicing? | 1. Single primary transcript can be spliced into different mRNA's by inclusion of different sets of exons. 2.During evolutionary history,various combos of exons may have been created due to exon loss. |
| What happens to the new viral proteins produced? | Alongside glycoproteins and nuclear material it is assembled into new virus.The new virus bud out of T cell taking some of host cell surface as their envelope and killing the cell as they leave. |
| What happens when the no. of viruses increase? | The no. if host T helper cells decrease; loss of T helper cells res. in macrophages, B and T cells not being able to be successfully activated therefore not functioning properly causing the persons immune system to become deficient. |
| What happens at the acute phase(when a person is first infected) of HIV? | HIV AB appear in blood after 3-12 wks |
| What are the symptoms for the acute phase? | Infected person may exp. e.g fever,sweats,headache,sore throat & swollen lymph nodes |
| What happens after? | Rapid rep.of virus & loss of T helper cells. After few wks. inf. T helper cells are recognised by T killer cella; which start to destroy them. This reduces rate of virus rep but doesn't eliminate it. |
| What happens at the chronic phase(latent)? | Virus cont. to reproduce rapidly but kept in check by immune system. |
| What happens in this phase? | 1. No symptoms exp., but an increase in tend. to suffer colds or other infections. 2. Dormant diseases like TB and shingles can reactivate. |
| Why does most HIV infections occur in dev. countries? | There is little money to provide drugs and do not have access to suff. food or clean water, therefore may go on to develop AIDS within a few yrs of infection. |
| What is the disease phase? | Increase no. of viruses in circ. & declining no.of T helper cells indicates AIDS.Decrease in T helper cells leaves IS vulnerable to other diseases.T helper cell count <200; therefore high risk of infection- opportunistic infection. |
| What opportunistic infections are found in people with AIDS? | TB and Pneumonia. There can be sig. weight loss and can lead to dementia. |
| What tumours are susceptible for those with AIDS? | Kaposi's sarcoma, which is identified as purple/black patches on the skin. |
| Where do diseases come from? | It has evolved from diseases of animals that have transferred to humans. Close contact increases chances of transfer from animals to humans. |
| How does the skin prevent entry of pathogens? | Keratin layer stops entry of MO's. Entry through wounds but blood clotting seals wound & reduces no.of MO's.Skin flora(large no.of microbes)live on skin surface,prevent col. of bacteria.Adapted to env. Other bacteria not suited to sweat,chem and sebum |
| What is sebum? | An oily fluid made by skin and can kill microbes/ |
| How does the mucous membrane prevent entry of pathogens? | Lines airways and gut provides easier routes into the body.As it is lacking any keratin, surface is moist therefore creating a favourable env. for bacterial growth. |
| How does the mucus and cilia limit entry of microbes to the lungs? | 1.The mucus which is sec. by the goblet cells in trachea and bronchi, traps microbes and other particles then beating cilia carry mucus up to the throat where it is swallowed. |
| How does the mouth, eyes and nose limit entry of microbes to the lungs? | As they secrete enzyme, lysozyme which breaks down bacterial cell wall causing cells to burst. |
| How does stomach acid limit entry of microbes to the lungs? | As gastric juices sec. by gastric glands in stomach walls contain HCl acid;giving a pH of <2. This kills most bacteria that enter with food but is opt.pH for d. enzyme pepsin which is secreted in gastric juices. |
| How does gut flora limit entry of microbes to the lungs? | N.flora benefit living within gut,cond.ideal warm,moist & food supplies.Host benefits,bacteria aid dig.process & comp.exclude pathogenic bacteria,comp.+ pathogens food & space.Bacteria sec.chem.l.acid;useful for defence against pathogen. Mutualistic.rel. |
| What are pathogens? | Organisms that cause diseases. |
| What is active natural immunity? | Exposed to antigen by getting the disease. Body produces memory cells which makes it immune to disease in the future. |
| What is active artificial immunity? | Injection of dead/weakened disease organisms, toxins or antigen fragments means that body is exposed to antigen and produces memory cells. |
| What is passive natural immunity? | A mother's antibodies cross placenta and are found in breast milk. These antibodies can protect against invading pathogen that mother has encountered. |
| What is passive artificial immunity? | When injected with antibodies that can provide immediate protection against invading pathogen they are specific for. |
| What must a vaccine contain? | 1.Attenuated virus;virus which has been weakened therefore harmless.E.g. measles vaccine 2.Killed bacteria;Whooping cough vaccines 3.Toxin; altered into harmless form e.g. Diphtheria virus 4.Antigen-bearing fragment of the pathogen e.g. Meningitis C |
| Why is it necessary to have a 'booster'? | To ensure long-time immunity. E.g.influenza which req. new vaccine every year to protect against new strains of virus. |
| How does vaccination help? | As not only does it protect the indv. it protects the community as disease will be less likely to be transferred therefore less disease in community. This group protection is called herd immunity. |
| What vaccine is used against Tb? | BCG vaccine. |
| What is the Heaf skin test? | 1.Extract from Tb bacteria is injected below skin using a ring of small needles 2.If area becomes red and swollen after 3 days,test is positive and therefore indv. has immunity to disease. 3.Therefore if negative, BCG vaccine is given. |
| What does the BCG vaccine contain? | Live chemically attenuated bacteria. |
| Who are usually vaccinated with BCG vaccine? | 1.Newborn infants(vaccinated withouy skin test) 2.Infants whose parents/g.parents were born in a country with Tb incidences 3.Prev. unvaccinated new immigrants from countries with high incidence of Tb. |
| What does Heaf test measure? | Immunity |
| What is the Mantoux test? | 1.Small amount of tuberculin is injected under skin 2.Reaction to test is viewed 48-72 hrs after injection. 3.If no reaction or only small lump forms, BCG is given. |
| What does Mantoux test detect? | Latent Tb infection |
| Why is it difficult to treat AIDS? | As virus is hidden inside T helper cells and the protein coat of HIV is constantly changing meaning that the Immune system cannot target and destroy it. |
| What are the two antiretroviral drugs which reduce production of more viruses? | 1.Rev.transcriptase inhib.;prev.viral RNA making DNA for integration into host's genome 2.Protease inhib.;inhibit proteases that catalyse cutting of larger proteins into small polypeptides for construction of new viruses. 3.Integrase and Fusion Inhib. |
| Why are the drugs given in combination? | As HIV can dev. resistance to anti-HIV drugs.Therefore if it becomes res. to one drug it may be susceptible to other drugs taken. |
| How can active Tb be killed? | By antibiotics. A combination of four antibiotic drugs are given for two months, with two cont. for a further four months. |
| What does this treatment ensure? | That any dormant bacteria is destroyed. |
| What is the name of Penicillin? | Penicillium notatum. |
| What was the bacteria being killed by the tiny droplets released from the mould? | Staphylococcus aureus. |
| What was the process Fleming discovered Penicillin? | 1.Found spot of green growing agar plate. He noticed there was a clear, bacteria free ring of agar gel around mould 2. More the mould spread the more bacteria killed 3.Mould produced tiny droplets of fluid on surface |
| How can Pencillin be made? | 1.Microbial fermentation 2.Semi-synthetic process which one antibiotic is converted to anothere |
| What is the process for this? | 1.Penicillium Chrysogenum grown,stainless steel fermenters cont.nutrient medium 2.Penicillin,released in fluid 3.Adj.pH end of Ferm.process causes penicillin to crystallise,then extracted 4.Immob.enzyme,penicillin can be mod.to range of novel penicilli |
| What diseases can Penicillin work against? | Pneumonia, Scarlet Fever. |
| What can it not work against? | On bacteria that causes typhoid or Tb. |
| What is the name of the antibiotic that cures tuberculosis? | Streptomycin |
| What are antibiotics? | A chem substance produced by microorganisms which has capacity to inhibit growth and to destroy bacteria and other microorganisms in dilute sol. |
| What do they do? | Help microorganisms compete in env. They are effective against bacterial cells but leave eukaryotic cells unharmed. However are useless against viruses. |
| What are the two types of antibiotics? | 1.Bactericidal; antibiotics that kill bacteria 2.Bacteriostatic; antibiotics that prev. multiplication of bacteria/slows the growth of bacteria. The host's own immune system can then destroy the pathogens |
| How can antibiotics be compared? | By clear zones[zone of inhib] around disks impregnated with various antibiotics. The wider the zone that remains clear due to no bacterial growth, the more effective the antibiotic is at prev.growth. |
| How can antibiotics interfere with bacterial cell growth? | 1.Inhib.b.cell wall syn,weak wall forms,lysis 2.Disruption of cell mem.changes in perm,lysis 3.Inhib.of n.acid syn,rep&transcip.Prev.c. division/syn.enzymes 4.Inhib.of Protein syn,enzymes&proteins x produced 5.Inhib.spec enzymes in b. cell,x host |
| Give examples of resistance? | 1.Sickle cell allele to malaria 2.CF allele to cholera 3.Tay-Sachs gene to Tb |
| What is the evolutionary race? | As quickly as we evolve mech. to combat pathogens, they evolve new methods of overcoming immune system. Sometimes pathogens have the edge in this race as their reproductive cycle is faster and pop. size is greater. |
| Why do bacteria pop. evolve very quickly? | 1.Rep.v.fast 2.Pop size large,no.of cells + mutations vast 3.R.mutation adv.Cell to use different food resources,reprod.quickly,infect other cells or produce sympt.in host e.g.coughing/sneezing. Bacteria,useful mutation,more likely to survive,rep & spre |
| How have mutations occured? | Due to selection pressures.E.g. human immune system; therefore evolution of bacterial strategies for evading or disabling immune system. |
| Why is it that Campylobacter is effective in evading host's cell surface membrane? | As it it has poor DNA repair system therefore genes coding for its surface proteins mutate freq. |
| How does M .tuberculosis and HIV evade the host's immune system? | 1.Waxy cell walls of M.tuberculosis allow bacteria to survive inside macrophages. They can also suppress activity of T cells. HIV invades T cells, prev. activation of macrophages,B cells and T killer cells; which weakens immune response. |
| What can occur in pathogenic bacteria to make them res.? | Mutations.Therefore the bacteria may produce an enzyme that is able to break down antibiotic or may use a different met. pathway for the reactions inhib. by antibiotic. |
| Why in the absence of antibiotic, bacteria may be disadvantaged? | As they may reproduce slowly using res. to produce enzymes that are not req. |
| How does antibiotics produce a sel. pressure? | As the bacteria x gene for res. are selected against, more likely to destroyed. Those that have gene selected for survive,grow and reproduce. Freq. of gene for res. increase and adv gene is passed on to generation; vertical evolution. |
| When does horizontal evolution take place in bacteria? | When the gene is passed from 1 bacterium to another; which may be of the same or different bacterial species. |
| What is a called when bacteria have cell-to-cell contact? | Conjugation. |
| What happens during conjugation? | A copy of a DNA plasmid can be transferred between cells. Antibiotic res. genes are usually carries on these small loops of DNA, so when plasmid is passed on the res. is transferred. |
| Why at the pres. of antibiotic will res. bacteria be adv? | 1.Survive with less comp. to reproduce rapidly |
| What is it called when a bacteria has evolved res. to sev. antibiotics? | Multiple-res. antibiotics. E.g. Staphylococcus aureus which can be controlled by vancomycin however showing signs of res. and evolving res. to new drugs. |
| How does the use of antibiotics when needed and ensuring course of treatment stop antibiotic res? | Reduces sel. pressure on organisms and destroys all bacteria causing infection. |
| How does isolating patients with res. diseases stop antibiotic res? | Prev. transmission of res. bacteria between patients |
| How does good hygiene incl. hand washing, ban on jewellery,ties and long sleeved shirts stop antibiotic res?? | Prev. spread of infection and cuts down on no. of places that may harbour pathogens. |
| How does screening of patients coming into hospitals stop antibiotic res? | A person may be infected without showing symptoms;can be detected and they can be isolated and treated. |
| How is prev. the dev. and spread of multiple-res. bacteria helped by? | 1. Antibiotics should only be used when needed 2. Patients should comp. course of treatment so all bacteria is destroyed 3. Infection control should be used in hospitals to prev hospital spreading |
| What creates mutations in bacteria? | Bacteria have a high rate of rep. therefore new mutations can occur reg. and each new mutation may help org. to survive. |
| What is the process of inv. bacteria and antibiotics? | 1.Sterile nutrient agar plate,seeded with suit. bacteria e.g.sterile spreader 2.Apply Antibiotic to sterile filter paper disc, lay on bacterial lawn using sterile forceps/place antibiotic sol into well in agar using sterile pipette. |
| What is the process of inv. bacteria and antibiotics?[2] | 3.Seal Petri dish, x tape all around dish 4.Incubate <30 for 24 hrs. 5.Look for clear areas around antibiotic discs or wells. Bigger areas ind. better antibiotic against bacterium species. |
| What is the process of antibiotic and bacteria? | 1. Some bacteria become res. to antibiotics which act as a sel. pressur due to random mutation 2.Antibiotic becomes inefficient 3.Therefore infections cannot be treated |
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