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Edexcel Snab Topic 3
The voice of the genome
| Question | Answer |
|---|---|
| What does a fertilised egg contain? | A complete set of instructions. |
| What is a genome? | DNA containing a full set of genes that control the growth and development of the whole organisms |
| How many genes do a human have? | 20000 - 25000 genes. |
| What do genes do? | Provide instructions to build and control a cell. |
| Where are Prokaryotic cells found? | Bacteria and Cyanobacteria, cell don't contain nucleus. |
| What are the features of a Prokaryotic cells? | -Infolding of Cell Surface Membrane - Plasmid(Small circle of DNA) - Slime Capsule, for protection and prevent hydration -Pili(Thin protein tubes, allow bacteria to adhere) -Flagellum: Hollow cyclindrical thread like structure, rotates to move cell. |
| What are the features of a Prokaryotic cells? [2] | -Ribosome -Circular DNA -Cell Surface Membrane -Cell Wall, peptideoglycan -Cytoplasm |
| What is the diameter of a Prokaryotes? | 0.5um-5um |
| What is the diameter of a Eukaryotes? | 20um+. |
| What is Mitocondrion? | An organelle which contains two membranes, which is folded to form cristae with matrix fluid; used for respiration.DNA as a loop. |
| What is Nucleus? | An organelle, enclosed by an envelope composed of 2 membranes, perforated by pores. Contains chromosomes & nucleolus. DNA Iin chromosomes contains genes that control synthesis of proteins. |
| What is Rough ER? | A system of interconnected membrane bound flattened sacs. Ribosomes are attached to the outer surface. Proteins made by ribosomes are transported through ER to other parts of the cell. |
| What is Ribosomes? | Made of RNA & protein, found in the cytoplasm or attached in Endoplasmic Reticulum. Site of Protein Synthesis. |
| What is Cell Surface Membrane? | Phospholipid bilayer containing proteins and other molecules, forming a permeable barrier. |
| What is Smooth ER? | Does not have attached ribosomes. Makes Lipids,Steroids (Reproductive hormones) |
| What is Golgi Apparatus? | Stacks of flattened membrane-bound sacs formed by fusion of vesicles from ER. Modifies proteins and packages them in vesicles for transport. |
| What is a Lysosome? | Sphereical sacs containing digestive enzymes and bound by single membrane. Involved in breakdown of unwanted structures within cells and destruction of cells. E.g. Acrosome. |
| What is a Centriole? | Hollow cyclinders made up of 9 protein microtubules, at Right angles. Involved in formation spindle during nuclear division & transport within cell cytoplasm. |
| Which organelles have 2 membranes? | Nucleus, Mitocondria, Chloroplasts, Amyloplasts. |
| What is Ultrastructure? | Name for the fine structure which is revealed when using power microscope. |
| What are the origins of chloroplasts and mitocondria? | Though to be independent prokaryotes, evolution of organisms they developed a mutualistic relationship. Theese gained protection and a more constant environment by being inside eukaryotes. |
| What does the movement of proteins involve? | Endoplasmic Reticulum and Golgi Apparatus and vesicles. |
| What is the production of proteins route? | 1.Transciption DNA to mRNA 2.mRNA leaves nucleus 3.Protein made,ribosomes,enter RER. 4.Moves through ER,3D shape 5.Vesicles pinched off RER contain protein 6.Vesicles from RER fuse,form flattened sacs of Golgi |
| What is the production of proteins route? | 7.Proteins modified /packaged in Golgi 8.Vesicles pinched off Golgi contain modifed protein 9.Vesicles fuses with cell surface membrane releasing protein |
| What are two types of gametes? | Sperm and Ovum |
| What does the cytoplasm of the ovum contain? | Protein and Lipid food reserves; for developing embryo. |
| What are some features of the sperm? | Much smaller, Motile, Long tail for it to be powered by energy release by Mitocondria. (ATP), Flagellum moves sperm along towards ovum. , Acrsome to penetrate Zona Pellucida. |
| What is the process of fertilisation? | Fusion of gametes. Males produce large number of sperm once they reached puberty, which enter vagina during intercourse swim through uterus walls. Sperm are attracted to chemical released by the ovum. |
| What happens when the sperm meets the ovum? | 1.Sperm reach ovum 2.Chemicals released surround ovum 3.Acrosome swells,fusing with sperm CSM 4.DE,acrosome released 5.Enzymes digest follicle cells & jelly layer 6.Sperm fuses/enters ovum 7.Enzymes released:lysosomes, 8.Nuclei of ovum/sperm fuse. |
| What happens when once the sperm fuses and penetrates membrane? | -Jelly layer hydrolysed -Sperm nucleus enters egg cell penetrated -Meiosis completes -Cortical granules,move towards egg cell surface membrane -Release enzymes -Zona pellucida hardens -X polyspermy -Egg nucleus envelope breaks down -Spindle fo |
| What are the plant gametes comprised of? | - Male; Stamen, Filament,Anther( where cells divide to produce pollen grains) which contain male nuclei. In female ovary; one or more ovules develop,contain female gametes, the ova. |
| How many chromosomes do humans have? | 46, 22 Homologous and 1 pair of sex chromosomes, Dogs have 78 and peas have 14. |
| What happens when gametes fuse? | The full number of 46 is restored. |
| What is mitosis? | Produces new body cells as an organism grows and develops. Retains diploid number.(2n) |
| What is meiosis? | Produces gametes with only half the number of chromosomes, haploid number (n) |
| Where does this happen? | In humans; ovaries and testes and in plants ovaries and anthers. |
| How are gametes formed | Chromosomes replicate before division. After replication each chromosome is made up of 2 strands of genetic material, 2 chromatids.Chromatids separate and gametes are formed, each with half the original number of chromosomes. |
| What is the importance in Meiosis? | To maintain diploid number after fertilisation and helps create genetic variation among offspring. |
| How does Meiosis result in Genetic Variation? | Shuffling of genetic material into new combinations. E.g Independent Assortment and Crossing Over. RANDOM |
| What is Independent Assortment? | -Random aligning of chromosomes -New combinations of parental chromosomes / alleles |
| What is Crossing Over? | -Breaking and rejoining of chromatids / DNA -Same chromosome pair; -Recombines genes / alleles,produces recombinants. |
| How does Fertilisation happen in mammals? | Nuclei from gametes combine, nucleus from one sperm enters ovum and Genetic material of the ovum and sperm fuse to form fertilised ovum; zygote. |
| What happens to Oscillin? | It is concentrated in the 1st part of the sperm to attach to ovum and enters before male nucleus in order to activate ovum. |
| How does Fertilisation in flowers take place? | Pollen lands on stigma & begins grow towards embryo sac. Pollen tube grows down style & secretes enzymes &digests style tissue & uses products continue tube growth.2 haploid nuclei are near tube tip. 1. pollen tube, control growth, 2.Generative nucleus. |
| How does Fertilisation in flowers take place? | Pollen tube reaches embryo sac, fuses whilst embryo sac breaks down.Generative nucleus divides to produce 2 male gametes. 1st male gamete fuses with female gamete(2n) and second male gamete fuses with 2 polar nuclei (3n) |
| What is a young shoot? | Plumule |
| What is a young root? | Radicle |
| What is Interphase? | Intense and organised activity during where the cell synthesises new cell componenets such as organelles and membranes and new DNA. Formation of new cellular proteins occus throughout . In S phase,DNA synthesis occurs throughout. |
| Which phase is more variable? | G1 |
| Where is cell division located in plants? | Meristem |
| Why are the nucleoli dark? | As ribosomes are formed there and they give a dark appearance. |
| What are Ribosomes made of? | Protein and mRNA |
| What happens to chromosomes in Interphase? | They unravel, allowing access to the genetic material enabling new proteins to be synthesised. Also it synthesises additional cytoplasmic proteins and organelles. |
| How are chromosomes organised? | In a DNA double helix, the DNA winds around proteins(hisotnes), then they form chromatin fibre. The fibre attaches itself to protein scaffold forming loops. The folding produces condensed chromosome structure. |
| How are genes controlled? | By supercoiling and repressor molecules. |
| What happens during Interphase? | -New organelles synthesised -DNA replication -Contains enough cell contents |
| What happens during Prophase? | -Chromosomes /chromatids condense become visible -Nuclear envelope breaks down -Nucleolus breaks down -Spindle (fibre) begins to form -Centrioles migrate to opposite poles |
| What happens during Metaphase? | -Chromosomes line up at the cell equator -Chromosomes attach to spindle fibres -Fibre attach at the centromere. |
| What happens during Anaphase? | -Spindle fibres contract -Chromatids / daughter chromosomes -Pull apart / separate -To kinetochore / centromere leads -Move to opposite poles of cell |
| What happens during Telophase? | -Chromosomes will be in the process of decondensing /uncoiling/ becoming invisible -Nuclear envelope is visible; -Nucleolus may be present -Spindle has contracted / broken down -Separate nuclei/masses of chromatin} now visible -Cell plate for |
| What is the role of the cell cycle? | -Growth and asexual reproduction. |
| What happens at Cytokinesis? | -Cell starts to separate. |
| What are the adaptations of an egg cell? | -Haploid,diploid number restored -Lipid droplets nutrients -Large cell SA,increased chance fertilisation -Zona pellucida,X polyspermy -Release chemical,attract sperm -‘sperm receptors’,surface,allows sperm to bind -mRNA present;TT |
| What does Mitosis ensure? | Genetic consistency, important in growth and repair and asexual reproduction. |
| How is this achieved? | -DNA replication prior to nuclear division -Arrangement of chromosomes on spindle and separation of chromatids to poles. |
| Where does this occur? | Growth of any organism and ensures all cells in the body have same genetic information. |
| What does Mitosis allow? | Old and damaged cells to be replaced with identical new copies. |
| What happens in Asexual reproduction? | Reproduce without producing gametes, growing copies of themselves by mitosis, producing offspring that are genetically identical to each other and parent. |
| How does this occur? | Through Binary fission, where bacterial cell grows and divides into 2 new cells. E.g. Hydra reproduce by budding. Common in plants too, where it is known as vegatative reproduction |
| Give some examples of organisms that can regenerate their bodies? | Hydra, Crown of throrns Strafish and Hyacinth bulb. |
| After a zygote has undergone all three complete cell cycles , how many cells does it contain? | 8 |
| What does Totipotent mean? | Can give rise to all 216 cell types (stem cells) are undifferentiated unspecialised -Can keep dividing |
| What does Pluripotent mean? | -Can give rise to many cell types -Cannot give rise to embryonic cells |
| What does Multipotent mean? | When cells retain a capacity to give rise to variety of different cell types. E.g. Neural stem cells, White blood cells from Bone Marrow,= |
| Suggest how a stem cell in the bone marrow can become a differentiated blood cell. | -Stimulus e.g. chemical -causes some genes active / some inactive in bone marrow stem cell -Only active genes are transcribed, mRNA made (only at active genes) -Protein made -Determine cell structure /function / permanently modifies cell |
| Explain how differential gene expression can enable cells which have the same genetic material to have very different structures and functions. | -Different genes active in different cells / different genes -Active at different times / some genes {active / inactive} -Active genes make mRNA -Active genes make proteins / polypeptides -Proteins control cell processes -Permanent change to cell |
| Why do Cnidarians have specialised cells? | Use for paralysing prey. Constantly replaced, therefore the Unpecialised cells which divide and differentiate when needed. |
| What is the use of dedifferentiating? | E.g. Garderners, ability to regenerate identical whole plant clones from roots, stem, leaf cutting. |
| What does Totipotency in plants allow? | Plants to be reproduced using plant tissue culture. |
| How is this process carried out? | Small pieces,plants are surface sterilised & placed on solid agar medium,nutrient,growth regulators. Cells divide,form a mass of undifferentiated cells,callus. |
| How is this process carried out?[2] | Altering growth regulators in medium, cells of callus, made to differentiate,form small groups of cells similar to plant embryo. Which develop into complete plants that are genetically identical clones. |
| What are the advantages of this? | -Large numbers of genetically identical plants -Done rapidly |
| Why can tissue culture also be important? | -Plant biology research , plant breeding , GM of plants & conservation of endangered plants |
| What is Differentiation? | Specialisation of cells. |
| Where is the main source of stem cells from? | Unused embryo's after IVF. |
| What are the Adv and Disadv of Embryonic Stem cells? | ADV: Easy to extract and grown DISADV:Ethical issues, possible rejection by patient's body, risk of infection when receieved, become cancerous in body. |
| What are the Adv and Disadv of Adult Stem Cells? | Adv:Fewer Ethical issues, Rejection risk avoided if taken from patient. Disadv: Difficult to extract, Difficult to produce different cell types, Risk of infection when cells extracted and received. |
| What are the Adv and Disadv of Fused cells? | Adv: Rejection risk avoided if nucleus taken from patient, Potential for treating genetic disorders. Disadv: Ethical issues with sources of embryonic nuclei, Risk of Infection when cells received, risk of stem cells becoming cancerous. |
| What are the uses of stem cells? | - Parkinson's disease - Multiple Sclerosis - Type 1 Diabetes - Burns |
| What is a potential for stem cells in the future? | Produce universal human donor cells, provide new cells, tissues, organs for treatment & repair by transplantation. Embryonic cells would be most suitable for this. They're potential to develop into any cell type offers great flexibility for development. |
| When Pluripotent stem cells be extracted from? | Spare embryo's. |
| What can the uses be ? | Research and Medicine |
| What is the process for this? | -Spare embryo's produced in fertility clinics, carry out IVF -Ovum is fertilised outside body-Women, given drugs to make them superovulate, producing more eggs -Some embryo's placed back in the womb and others are for embryonic stem cells. |
| What are the uses for embryo's for research? | Grow to form blastocysts and cultured for a further period of time, to see if stem cells are formed. Stem cells isolated from each embryo and rest discarded. -Then cultured an used in research . -In future used for transplantation |
| How would you resolve the problem transplant rejection? | Tissue typing, organs grown from stem cells, drugs that prevent recipient from rejecting any transplanted organs and therapeutic cloning. |
| What is a therapeutic cloning do? | - Patient needing transplant , would have one of their diploid cells removed. -Cell or nucelus would be fused with an ovum, which haploid nucleus had been removed. -Stimulated back to mitosis |
| What is somatic cell nuclear transfer used for? | To produce blastocysts, from which human stem stem cells are extracted. |
| What happens to animal embryo's? | The nucleus of animal egg is removed and human nucleus is fused with egg cell. |
| What is Embryonic stem cells used for? | Research into human development & disease; to explore how genes trigger onset of development. Can help us understand how cancer cells develop and how certain birth defects occur. |
| Where can in matters of science, can making new laws receive advice ? | Select committees in both Lords (Peers) and Commons(MP's) also expertises in the subject. For foods with GM ingredients, the Advisory Committee on Novel Foods and Processes. Mainly made up of scientists and also an ethicist. |
| What decision do scientists make? | An objective interpretation of scientific evidence, understanding in the field. |
| How can other members help make decision? | By providing an alternative points of view. |
| Who makes the final decision? | The HFEA. |
| What does the law state about the use of human embryo's? | -Promote adv in treatment of infertility -Increase knowledge about causes of congenital disease -Causes of marriage -Develop more effective methods,contraception -Develop methods,detecting gene/chromosome abnormalities in embryo's before implantation. |
| What are stem cells? | Undifferentiated cells; which can keep dividing and can give rise to other cell types. |
| How did cloning take place?[Dolly the sheep] | Nucleus from mammary gland cell of one sheep transferred into enucleated egg cell of another sheep (SCNT). The resultant diploid cell divided to form an embryo which was implanted into an adult sheep who gave birth to dolly. |
| Why may cloning mammals have such a low success rate? | DNA in adult cell nucleus has been programmed into particular type of cell.E.g.skin cell. When transferred to ovum, nucleus may not be able to reprogram it's DNA quickly enough to be able to switch on all different genes required for gene development. |
| What happens when an embryo develops? | Cells differentiate & become specialised.Structure & function of each cell is dependent on proteins that it synthesises.E.g. Slavary gland cell make salivary amylase,enzyme,digesting starch; red blood cells contain haemoglobin,oxygen carrying pigment. |
| How is it that these cells produce only these proteins? | As different specialised cells must only be expressing some of their genes. |
| What was the experiment Igor Dawid and Sargent carried out? | -Extracted mRNA from differentiated & undifferentiated frog cells. -cNA strands were produced for all the mRNA in the differentiated cells, using enzyme reverse transcriptase.(Reverses transcription) makes DNA from mRNA. |
| What was the experiment Igor Dawid and Sargent carried out?[2] | -cDNA strands mixed + mRNA,undifferentiated cell. Complementary strands of cDNA & mRNA combined to make hybrids. Hybrids separated out,remained a range of cDNA strands,not been hybridised; 2 cells were expressing some of same genes,also different genes. |
| Why did they carry this experiment out? | To demonstrate that different genes are expressed in different cells. |
| What was the method called? | Subtractive mRNA hybridization, that allowed them to quickly look at genes expressed by different cell types. |
| Why did they use Frogs? | As they have specific stages of development? |
| What happens at the Gastrula stage? | The ectoderm,endoderm and mesoderm layers develop. |
| What is a Blastula? | A ball of undifferentiated cells. |
| Therefore why only some cells become specialised? | Only some genes are switched on and produce the active mRNA which is translated into proteins within the cell. |
| What experiment did Jacob and Monod carry out? | They first to propose a theory for control of gene expression. Studies the control of genes in E-coli. (Bacteria) Which produced an enzyme called B-Galactosidase, to break down Lactose when present. Enzyme converts lactose to glucose and Galactose. |
| What experiment did Jacob and Monod carry out? [2] | Lactose X present,lactose repressor molecule binds to DNA,prevents transcription of B-G gene being expressed. Lactose present, Repressor molecule prevented from binding to DNA & B-G is expressed. mRNA coding for B-G is transcribed and translated. |
| What switches an individual gene on or off in Eukaryotes? | Uncoiled genes,transcribed into mRNA. Enzyme mRNA polymerase binds section of DNA adjacent to gene to be transcribed, promoter region.When enzyme has attached to DNA, transcription proceed. Gene switched off until enzyme attaches to promoter region. |
| How can transcription of gene be prevented? | Supercoiling or Repressor molecules(attaching to promoter region, blocking the attachment site. |
| What is an example of gene expression going wrong? | FOP- growth of bones on odd places e.g. muscle and connective tissue. Leads to freezing of major joints of backbones and limbs; they cannot move. Even injection of medicines into muscle, cause bone formation in people with FOP. |
| What is FOP caused by? | Inherited condition,by a gene mutation. Genes X switched off in White blood cells. Tissue damaged,injecttion,White blood cells move to damage,produce protein,diffuses into muscle cells.Protein causes muscle,express other genes,turn into bone cells. |
| How are cells organised into tissues? | Cells,specific recognition proteins, adhesion molecules on cell surface membrane. Help cells recognise other cells,themselves & stick to them. Part of each recognition protein is embedded in cell surface membrane, large part extends from membrane. |
| How are cells organised into tissues? | Exposed section binds to comp proteins ,adjacent cell.Particular recognition proteins synthesised by cell, determine which cells it can & X attach to.Cells from different tissues separated then mixed; reform into tissues as Recognition proteins bind. |
| Give an example of a extracellular matrix which is a major component tissue? | Cartilage. |
| What is a cell? | In multicellular organisms, cells are specialiased for a particular function.E.g. muscle cells and epithelial cells. |
| What is a tissue? | A group of specialised cells working together to carry out one function. E.g. muscle cells forming muscle tissue. Epithelial cells forming Epithelial tissue. |
| What is an organ? | A group of tissues cells working together to carry out one function.E.g. muscle,nerve and epithelial work together in the heart. |
| What is an organ system? | A group of organs working together to carry out particular function E.g. circulatory system. |
| What determines the sequence of changes during development? | Precise sequence of transcription and translation of genes. |
| How have researchers found out how genes determine structures produced during development? | Studying embryonic development of model animals and plants. |
| What control the development of each segment in fruit flies? | Master genes; discovered by looking at mutations which cause wrong appendage for segement. Master genes produce mRNA; translated into signal proteins Proteins switch genes responsible for producing proteins needed for specialisation of cells in segment. |
| What part of the plants becomes specialised to form parts of the plant? | Meristem. |
| How does the plant, Arabdiopsis thaliana help? | To model what is happening when plants change form vegetative growth to reproductive growth. |
| How are the floral organs placed? | In concentric whorls. |
| What do master genes do? | Produce mRNA that codes for signal proteins which switch appropriate genes. Synthesis of these proteins coded for, results in development of specilised cells. |
| What is cell death called? | Apoptosis, programmed. |
| What is phenotype? | Outward expression of a cell or organism due to interaction of genotype environment. |
| What is discontinous variation? | Phenotype of an organism is almost entirely due to the genotype, the phenotypes present in a population fall into discrete groups with no overlap. E.g. Blood groups. |
| What is continous variation? | Characteristics that are affected by both genotype and environment, e.g. height.Controlled by genes at many loci, polygenic inheritance. |
| What are Blood groups due to? | Blood groups -due to antigens on surface of red blood cells,Controlled by gene with three alleles (A,B and O) which interact to produce only four blood group phenotypes, A, B, AB and O. The blood group phenotype depends entirely on the genotype. |
| What is Polygenic Variation? | More than 1 gene,involved in influencing the phenotypes. Give rise to contionous variation , few extremes & many in the middle E.g. Bell shaped curve. E.g. eye colour, alleles at different loci control eye colour. Also height, weight & skin pigmentation. |
| What is gene loci? | Genes will be at different locations on chromosomes. |
| What happens in monohybrid inheritance? | Each locus is responsible for a different heritable feature. |
| What happens when more than 1 gene is involved? | Greater the number of possible genotypes & phenotypes & greater the range of variation for character in population as a whole. Range of variation,increased by environment expression of the genes e.g. diet alters weight, exposure to UV alters skin colour. |
| What are 4 examples of influence of the environment and genotype on phenotype? | Human height Animal hair colour Cancer An enzyme called MAOA and behaviour. |
| What are the possible causes of increase in height? | -Taller men have more children;gradual change in the genetic make-up of population -Greater movement of people, less inbreeding - to taller people -Better nutrition, increased protein;greater growth |
| What are the possible causes of increase in height?[2] | -Improved health, reduction in infectious diseases,sanitation, clean water supply, vaccination and antibiotics -End of child labour, -Better heating of houses and better quality of clothing, less energy lost keeping warm,more energy,put into growth |
| Why may someone with potential(genetically) to become tall, may not reach their not reach their potential? | Due to malnutrition. Nutrition is important as more food available, quality of food better so more protein for more growth, calcium and vitamin D, essential for bone growth |
| What is hair pigmentation due to? | Melanin. |
| Where is melanin made? | In melanocytes,found in skin & root hair follicle,activated by MSH; Receptors found on surface of melanocyte cells. Which place the melanin in organelles; melanosomes. Collect around nucleus Protecting DNA from UV. More receptors, more protection. |
| What does UV to do MSH? | Making them more active and therefore making skin darker. Binds to MSH receptors in membrane of melanocytes |
| What happens next? | Results in activation of transcription and translation of the gene for synthesis of an enzyme called tyrosinase, which synthesises melanin and then it accumulates in melanosomes produced by the Golgi body. |
| What does Tyrosinase do? | Catalyses the first step along a chemical pathway, changing amino acids tyrosine into melanin. |
| What can UV do to DNA? | Distortion in DNA and affects replication and transcription- Thymine Dimers[Distortion of helix] |
| What happens when there is exposure to UV light? | -melanocytes enlarge, -more branched, -more MSH receptors -so more melanin and melanosomes produced; darkening of skin |
| Therefore how does genotype and environment both play a role in this? | Genotype determines number of MSH receptors to determines amount of melanin that can be produced. Environment i.e. amount of UV determines how much melanin is actually produced |
| What happens to Arctic foxes in summer? | They become brown.(more melanin). Foxes produce few MSH receptors in summer,no any MSH produced has no effect(no receptors to bind to so no tyrosinase produced so no melanin made. |
| What happens to Arctic foxes in winter? | They become white.(less melanin). |
| What happens in Himalayan rabbits? | They have an allele of the tyrosinase gene which produces an enzyme which is inactivated at normal body temperature. Extremities – tips of ears, nose, paws – are much darker than the rest of the animal |
| What happens in Himalayan rabbits?[2] | In the warmer parts of the body tyrosinase is denatured so no melanin is produced and the hair is white. The extremities of the body are slightly cooler so the tyrosinase enzyme remains active so melanin is made so the tips are darker. |
| What is MAOA? | MAOA = monoamino oxidase This is an enzyme that catalyses the breaks down neurotransmitters (dopamine and serotin)in the brain involved in the nerve pathways that control behaviour. Found in X chromosome. |
| What happened when some people had a mutation in their MAOA gene? | Had become aggressive. |
| What is the Dunedin study? | Interation between MAOA genotype & child mistreatment&antisocial behaviour.1000 children from Dunedin, over 20 years. 2 alleles for MAOA gene; High/Low level of enzyme production. Maltreated children with MAOA,displayed less anger then those without MAOA. |
| What causes cancer? | Rate of cell multiplication is faster than cell death, causes a tumour; high rate of mitosis. Caused by damage to DNA e.g. UV and asbetos, chemical e.g. carcinogens- From environment or cell metabolism. |
| How can inherited cancer be formed? | If DNA is copied incorrectly in gamete formation. |
| What happens in the cell cycle? | Proteins are produced that stimulate next stage in each cycle. Cells also produce proteins that stop the cell cycle, preventing progress from one stage to the next. These proteins activate/ inhibit enzymes that initiate reactions. |
| What are the 2 types of gene that have a role in control of cell cycle and play a part in triggering cancer? | - Oncogenes -Tumour Supressing Genes |
| What do Oncogenes do? | Code for proteins that stimulate the transition from one stage in cell cycle to the next. Mutations in these genes can lead to cell cycle being continually active, can cause excessive cell division- tumour. |
| What do Tumour Supressing Genes do? | Produce supressor proteins that stop cycle . Mutations inactivating these genes, no brake on cell cycle. E.g. p53; protein stop cell cycle by inhibiting cells a lack of p53; cell cannot stop entry into s phase. |
| Why is cancer more likely to occur in older people? | Accumulated more mutations. |
| What can many gene defects lead to? | Bowel, Ovarian , Prostate, Retinal cancer and some types of leukaemia. |
| What can loss of tumour suppressor proteins lead to? | Skin, Colon, Bladder and Breast cancer. |
| What is the mutation in the gene for Breast cancer? | BRCA1 gene produces a protein used to repair DNA. |
| What does it mean if you have this BRCA1 gene? | That someone is more susceptible to cancer through environmental damage. |
| What are chemical factors from the environment to get cancer? | - Smoking, increases chance in cancer e.g. lung cancer. Tar lodges in bronchi and causes damamge to DNA in surrounding epithelial cells. |
| How can UV be a physical factor? | - Damages DNA in skin cells, mole may develop into a tumour. If tumour not removed, may spread to other parts; carried by blood or lymphatic systems. |
| How can diet help prevent cancer? | Provides antioxidants can help destroy radicals. |
| How can Virus Infection trigger cancer? | Lung caner from Hepatitis and Cervical Cancer from infection by Papilloma virus. It may also contain Oncogene in mRNA, transfers to the cells. |
| What is a way of getting rid of cancer? | -Surgically removed -Chemotherapy -Radiotherapy This DNA damage can cause the release of the protein p53, to stop cancer cells dividing. |
| What is Hammerling's experiment process? | -Hats removed & stalks swapped -Plants develop hats with features of both species. -Intermediate hats removed, new ones grow that correspond to nucleus in rhizoid. Demonstrates role of nucleus & chemical messengers in development of cell. |
| What is the advantages of using an Acetabularia [green alga]? | - It is large and therefore easy to dissect and perform experiments on. |
| In the Acetabularia ,what parts are able to regenerate parts of the cell? | The Rhizoid and tip. Also when rhizoid is left attached to stem a new tip, capable of developing a hat is produced; through a chemical signal. as an electric signal could not pass once cut off. It states that the nucleus controls developement of the cell. |
| What is Hammerling's experiment process with both Acetebularia meditteranea and Acetebularia crenulata? | m |
| From the results of Experiment 1, what can you conclude about the position of the genetic material in the Acetabularia cell? | The genetic material could be in the rhizoid or in the tip, as both of these sections of the cell are capable of developing other parts. |
| Does Experiment 2 give you any evidence that either backs up or conflicts with the conclusions you drew from Experiment 1? | Stem is able to develop a hat after being attached to the rhizoid for a few days after the removal of the original hat, Experiment 1 stem unable to develop a hat.Rhizoid influences development in the tip of stem, genetic material is in the rhizoid. |
| What extra information does the result of Experiment 3 give you that supports or modifies your answer to 1? | The nucleus, and not the rhizoid, appears to control development. |
| What can you conclude from Experiment 4 about what influences development of the tip of the Acetabularia cell? | The development of an intermediate hat suggests that there is an influence such as a chemical messenger that accumulates at the tip. This influence was still affecting hat development after the stem transfer. |
| Explain how Experiment 4 supports the conclusions made from the first three experiments | The development of the hat characteristic of the species of the nucleus present, after removal of the intermediate hat, shows that the nucleus controls the characteristics of the cell. |
| Outline the ‘story’ of how the nucleus in the rhizoid of Acetabularia controls cell processes at a distance, such as development of a new hat | Transcription DNA in nucleus,mRNA;moves from nucleus cytoplasm. Translation of mRNA on ribosomes,proteins,new ‘hat’ mRNA ’messenger’ moves to tip,protein synthesing; growth of‘hat’.Proteins synthesised close to nucleus&which move to tip,growth of the ha |
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