molecular virology

Question 1

psuedorevertant

Answer 1

a wild type phenotype from a virus that is still genetically mutant

Question 2

mutant viruses cab revert to their original phenotype in 3 ways

Answer 2

back mutation intragenic suppression extragenic suppression

Question 3

genetic interactions in viruses

Answer 3

1.complementation-describe two types:allelic-different mutatnts have complementing defects in the same protein non-allelic-mutants with defects in diff genes. Recombination-physical interaction of virus genomes in a superinfection resulting in gene combinations not present in neither parent. can be done by strand breakage and religation or copy choice. Reassortment.-random shuffling of genome segments during a superinfection.Frequency of recombination can be high-indicating that markers are on two different segments or low -markers are on the same segment.

Question 4

non genetic interaction between viruses

Answer 4

interference phenotypic mixing pseudotyping.

Question 5

herpesviridae

Answer 5

linear,doubke stranded DNA

Question 6

parvovirus

Answer 6

linear ,non segmented single stranded Dna has two genes:rep-encodes proteins involved in transcription cap-encodes coat proteins

Question 7

polyomavirus genome

Answer 7

double stranded circular dna

Question 8

positive strand RNA viruses

Answer 8

picornavirus,togavirus,flavivirus,coronavirus

Question 9

negative strand RNA viruses

Answer 9

bunyavirus,arenavirus,orthomyxovirus,paramyxovirus,rhabdovirus

Question 10

main difference between retrovirus and retrotransposon

Answer 10

additional gene in retroviruses ;env gene that encodes for envelope glycoproteins

Question 11

unique features of retroviruses

Answer 11

-only viruses that are diploid only virues that require specific cellular RNA (tRNA) for replication only viruses whose genome is produced by cellular transcriptional machinery. only + sense rna viruses whose genome doesnt serve directly as mRNA immediately after infectiob

Question 12

polyomaviruses

Answer 12

heavily dependant on cellular machinery for both replication amd gene expression. they encode T-antigens that stimulate transcription. papillomaviruses dependent on cell for replication.

Question 13

Adenoviruses

Answer 13

dependent on cellular apoaratus for transcription ,independent for gene expression. some mechanisms for gene expression:trans-acting transcriptional activators -E1A protein and post transcriptional regulation of expression.

Question 14

herpesviridae

Answer 14

less reliant.Encode many enzymes involved in DNA metabolism and several trans-acting factirs that regulate the temporal expression of virus genes contrling phases of infection.

Question 15

poxvirus

Answer 15

almost independent expect for host cell ribosomes.Also encode numerous enzymes involved in dna metabolism