mutagens
physical or chemical agents that can cause mutations
average mutation rate in humans
2.5 x 10^-8 mutations per nucleotide (175 mutations per diploid genome per generation)
types of point mutations
base-pair substitutions - replaces one nucleotide and its partner with another pair of nucleotides
insertion or deletions - additions or losses of nucleotide pairs in a gene
*more severe effect!
types of base-pair substitutions
silent mutations - no effect on amino acid because of redundancy in genetic code
missense mutations - still code for an amino acid, but not necessarily the right amino acid
nonsense mutations - change codon into stop codon, nearly always leading to a nonfunctional protein
info on insertions/deletions
- can have a disastrous effect on protein
- may alter the reading frame, producing a frameshift mutation
- can occur during DNA replication, recombination, or repair
what are the effects of DNA damage and mutations?
- developmental abnormalities
- senescence
- apoptosis
- tumors
emergence of a variant in a population
- pop. initially dominated by one form of virus
- random variants exist at low levels or develop spontaneously
- variant gains competitive advantage due to natural selection (can coexist with initial form or become dominant)
- new variants can continue to emerge
consequences of new gene variants
- variant may spread more quickly, cause more severe disease, and may be more deadly
- virus may evade diagnostic tests
- variants may be more resistant or immune to therapies
- may gain ability to escape recognition by immune system, making vaccines and natural immunity not effective
