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BIO 201 Exam 2 Ch 10
Viruses
| Question | Answer |
|---|---|
| what are viruses? size? | -obligate intracellular parasites -20nm - 200nm (much smaller than prokaryotes) -not seen by light microscopy |
| what is the structure of viruses? | -very simple structure -nucleic acid (DNA or RNA) enclosed by capsid (crystalline protein coat) -capsid surrounded by membrane (envelope) -protein spikes (hemaglutinin) on membrane |
| what is unique about viruses entry? | -host and tissue specific -dock with cellular receptors = gain entry |
| describe the relationship of chromosomes and DNA in viruses | -DNA or RNA (not both) -single-stranded or double-stranded -chromosomes very few genes (20-50) |
| how do viruses replicate themselves? | -through 2 processes called the "lytic cycle" and "lysogenic cycle" of a bacteriophage (a virus that attacks bacteria) |
| what are the first 3 steps to the lytic cycle? | 1) the bacteriophage attaches to bacterial cell injects DNA 2) DNA codes for proteins. the first proteins shut down metabolism (get ready to make more viral components) 3) DNA replicated capsid proteins produced |
| What are the last 3 steps to the lytic cycle? | 4) DNA, capsid protein self assemble produce complete viruses 5) enzyme produced by virus breaks cell open 6) viruses escape to infect other cells |
| how many viruses are produced at each infection? | between 10 and 1000 viruses |
| what is the lysogenic cycle? | -different bacteriophage life cycle (1 of 2) -the same bacteriophage can follow either the lytic or lysogenic cycle |
| what are the first 2 steps of the lysogenic cycle? | 1) the bacteriophage attaches to bacterial cell wall injects DNA 2) DNA integrates into the bacterial chromosome |
| what are the last 2 steps of the lysogenic cycle? | 3) infected bacterium grows and multiples (often for years) 4) when cell stressed the viral DNA exits from host chromosome initiates the lytic cycle |
| how are animal viruses propagated? (first 2 steps) | animal viruses propagated in appropriate host cell 1) virus attaches to host cell via docking receptor. endocytosis occurs 2) in cytoplasm capsid coat is removed |
| how are animal viruses propagated? (last 2 steps) | 3) DNA & RNA synthesis occur --> protein synthesis 4) virus self-assembles. budded off from cell by exocytosis |
| what are the three viral types and what do they mean? | -3 types A,B, and C -A and B are the major types -A is the most dangerous |
| what is influenza? | -self-limiting infection |
| what are the troubles of influenza and immunity? | -antigenic variation prevents immunity -vaccine administered every year |
| how is influenza prevented? | -anti-viral drugs -acetominophen PROLONG recovery |
| what are measles? how is it spread | -highly-contagious infection in children -spread by direct contact and aerosols |
| what are the symptoms of measles? | -harsh cough -runny nose -white spots on gums and inside cheeks -Koplik's spots on the palate - red spots with dark centers |
| how does measles spread through the body? | -spreads through lymphoid tissue -a reddish brown rash progresses from the face > trunk > arms and legs -may include conjuctivitis |
| what are some possible complications of measles? (can cause?) | pneumonia & encephalitis |
| how is measles prevented? | -NOTE: the patient permanently IMMUNE after infection -MMR vaccine |
| what is Hepatitis A? | -acute viral infection of the liver |
| how is Hepatitis A transmitted? | -through water and food -especially raw foods and unpasteurized fruit juice |
| how is Hepatitis A prevented? | -vaccine called Havrix -NOTE: childhood exposure to HAV reduzes asthma incidence in adults |
| what is hepatitis B? | -chronic viral infection of the liver |
| how is hepatis B transmitted? | -primarily parenteral (injection) -sexually transmitted among gay men -sweat in contact sports, tattoos |
| how is hepatits B prevented? | -a recombinant vaccine HAV-HBV is available |
| what is papilloma? how is it transmitted? | -one of most common STD viruses in US -affects skin and mucous membranes (tree man) -sexually transmitted, also prenatal infections |
| what are the symptoms of papilloma? | -warts on cervix, vulva, perianal, and mouth (cauliflower shaped) -itching, burning, and pain -infection is PERMANENT |
| how is papilloma treated? | -treated by cryosurgery, electrocautery -medications - trichloroacetic acid (TCA), 5-Fluorouracil (5FU) |
| what is adenovirus? | -a group of viruses that cause respiratory illness including -sore throat -bronchitis -colds -pneumonia |
| how are adenoviruses transmitted? | they are transmitted orally and via aerosols |
| what is unique about the infection of adenoviruses? | -the infection is self-limiting -symptomatic treatment is the recourse |
| what other disease can be caused by adenoviruses? how are they controlled? | -gastroenteritis -conjuctivitiy -both controlled through chlorination in swimming pools -Ad-36 linked to extreme obesity |
| what is the cause of genital herpes? | -it is caused by Herpes Simplex Virus type 2 (HSV2) -it is sexually transmitted |
| what is the result of genital herpes? symptoms? | -PERMANENT infection in the nerves -symptoms are painful sores, blisters, lesions and ulcers on genitals/anus (infectious) -foot sores in neonates |
| what are the dangers of genital herpes and pregnant women? | -virus can pass to fetus -resulting in miscarriage -mental retardation -hearing loss -during birth newborn may show herpetic lesions |
| what is Kaposi's sarcoma? | it is a cancer of the skin caused by Herpes simplex virus type 8 (HSV8) |
| how does Kaposi's sarcoma result? | -result of a compromised (weakened) immune system -15x higher in males |
| what is Varicella/Zoster? how is it caused? | -varicella (chickenpox) -caused by Herpes simplex virus 3 (HSV3) |
| how contagious in varicella? | -highly contagious -95% of people contract during childhood |
| what are the symptoms of varicella? | -itchy rash, blisters -scabs trunk, face > all over -fever and malaise |
| what complications does varicella have? | -virus remains dominant in sensory ganglia after infection, can be reactivated in old age (>50% age 80+!) |
| how does pain arise in varicella? | pain arises from nerve damage |
| what is postherpetic neuralgia? | pain from nerve damage, crusted lesions that continue to hurt in varicella patients and (highly sensitive to cold and heat) |
| how is varicella prevented? | -adult varicella vaccine -NOTE: blacks significantly lower risk of varicella due to unknown genetic mechanisms |
| what is SARS? | -Severe Acute Respiratory Syndrome -virus belonging to coronoavirus ("corona" surrounding the virus) |
| what kind of viruses is SARS related too? | related to viruses from wild animals and birds |
| what are the dangers of SARS? | it mutates very rapidly and is highly contagious |
| how is SARS transmitted? | -transmitted by droplets as well as contaminated surfaces -bats > civets > humans |
| what are the symptoms of SARS? | -general discomfort -high fever -malaise -possible diarrhea |
| how is SARS diagnosed? treated? | -DNA methods and electron microscope -no cure or vaccine however it is qurantineable |
| what are retroviruses? | -family of single-stranded RNA viruses that cause cancer, leukemia, and AIDS |
| what is a central characteristic of retroviruses? | -presence of an enzyme called "reverse transriptase" within the viral capsid -required for viral pathogenesis |
| how does the process of retroviruses work? | during infection, single-stranded RNA chromosome must be copied to make DNA replica |
| what are the first 2 steps of the retrovirus process? | 1) reverse transcriptase makes a single-stranded DNA copy of RNA 2) the RNA is removed leaving single-stranded DNA |
| what are the last 2 steps of the retrovirus process? | 3) the single-stranded DNA is copied to make a double-stranded DNA 4) the viral DNA chromosome integrates into the host chromosome (permanent, cannot be reversed) |
| what is the complication of retroviruses? | retroviral diseases can only be SLOWED by drugs if infected tissue not rid of entirely |
| what are ERVs? | -endogenous retroviruses that exist in mammalian chromosomes |
| why are ERVs important? | they appear to have led to the evolution of placental mammals |
| what is a mimivirus? what is special about it? | -mimivirus contains ~1200 genes (2x smallest bacteria) -infects protozoa -it is an exception -contains DNA and RNA -capsid proteins AND ribosomes -host takeover DNA/RNA synthesis -attacked by Sputnik (50nm virus) requires mimivrus components to repl |
| what is a megavirus? | -larger than mimivirus -o.7 micrometers, infects protozoa -has fibrils, like mimivirus |
| what is important about the mimivirus and megavirus? | -share a common bacterial ancestor -behave as viruses due to loss of genes |
| what are the major complications of papilloma? | -major cause of cervical cancer |
| how can papilloma be prevented? | -vaccine 100% effective if given <9yo, before sex -circumcision prevents males from HPV -multiple partners increases risk |
| what is HSV1? what does it cause? | -herpes simplex virus 1 -causes cold sores linked to Alzheimers disease (70% of patients have HSV1) |
| what is the difference between lytic and lysogenic cycle? | -lytic cycle -host cell killed at end -lysogenic cycle - host cell survives |
| what can stress a cell in lysogenic cycle? | heat, shock, UV |
| what are the symptoms of influenza? | -fever, sore throat, runny nose, fatigue and myalgia |
| what are the dangers of influenza in elderly patients? | pneumonia may result --> death |
| what are the hepatitis a symptoms? | -icterus (jaundice)(yellowing of skin and eyes) -nausea, loss of appetite, and fatigue |
| what are some hepatitis b symptoms? | -jaundice, nausea, appetite loss, fatigue |
| what are the stage 2 hepatitis b symptoms? | -symptom free chronic infection -cirrhosis, liver failure, and liver cancer |
| who is at risk of hepatitis B? | health workers, injection drug users, hemodialysis and blood transfusion patients |
| what can Kaposi's sarcoma affect? | -affect the skin, internal organs in AIDS patients |
| what two groups are involved in complications of varicella? | -old age (produces shingles) -can infect fetus > 2x risk of cerebral palsy -arthritis meds increase risk |
| what are some serious symptoms of SARS? | -2-7 days later - dry cough, pneumonia, and death |
Created by:
rolandowallace
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