Lecture 6 2/6/24 Flashcards
What is virus evolution?
-genomic changes in hereditary genomes that may result in phenotypic changes
-occurs within a viral population
Why is it important for mutation rate to be balanced?
-too high of a rate results in defective progeny
-too low of a rate does not allow progeny to adapt to changing environment
Why do RNA viruses tend to have more mutations than DNA viruses?
-higher error rates and lower stability
-viral polymerases lack proof-reading mechanisms
What are “hot spots”?
certain positions in viral genomes that have higher mutation rates
What are the characteristics of selection pressure?
-does not cause mutations
-selects for already existing mutants
What is a mutation?
change in the base sequence of a nucleic acid resulting in the alteration of the resulting protein
What happens when mutations occur in less tolerant proteins?
results in a non-infectious virus
What are the three types of drift/point mutations?
-silent
-substitution
-nonsense
What is a silent mutation?
mutation within a codon that produces the same viral protein sequence
What is a substitution mutation?
mutation within a codon that produces a different viral protein sequence
What is a nonsense mutation?
mutation within a codon that leads to the cessation of the viral protein sequence
What is a conservative substitution?
when a different amino acid is substituted, but it has similar properties to the original amino acid
What is a non-conservative substitution?
when a different amino acid is substituted that does not have similar properties to the original amino acid
What is a deletion mutation?
-deletion of nucleotides
-causes a frameshift mutation
-changes amino acid sequence downstream of mutation
What is an insertion mutation?
insertion of multiples of 3nt bases to a viral gene, resulting in the addition of amino acids
Which type of mutation is easy to revert back to wildtype?
point mutations