Evolution of Genes and Genomes Flashcards
Raw material for evolutionary change
mistakes in DNA replication/repair
point mutation
single base pair mistake
substitution
point mutation goes to fixation in a population
Synonymous
substitution does not change the amino acid
silent subsitution
nonsynonymous
does cause a change in the amino acid specified
in synonymous substitutions, fate of the mutant allel goverened maiinly by
drift
iin nonsynonymous substitutions, fate of the mutant allele in large populations iis governed mainly by
selection; depends on advantageous or deleterious
N/S = 1
neutral in respect to fitness
N/S >1
under positiive selection for change
N/S< 1
an amino acid position is under purifying selection
molculer clock hypothesis states that
DNA and protein sequences evolve at a rate that is relatively constant over time and among different organisms
direct result of rate constancy between DNA/protein sequence evolution and time
genetic difference between any two species is proportional to the time since these species last shared a common ancestor
genome
full set of genes plus noncoding regions of DNA
nucleoid/plasmid
prokaryote genes
mitochondria/chloroplast
eukaryote genes
two ways new genes could be acquired by a genome
duplicating existing genes
acquiring from another species
autopolyploidy
can create new species in a single generation
limit of autopolyploidy
individuals cannot mate with individuals that have same number of chromosomes as their parents
polyploid organisms
have more than two complete sets of chromosomes
gene duplications
may give rise to new protein functions
4 types of gene duplications
- one is nonfunctional
- one gets substitutions and new function
- both have original function but expression diverges
- both retain original function
pseudogenes
no longer functional genes
types of mutations on pseudogenes
neutral
hemoglobiin genes in humans
are expressed at different stages of development