Molecular Evolution Flashcards
What is the start codon?
ATG
What are the three possible stop codons?
TAA
TGA
TAG
What are non-synonymous nucleotide substitutions?
Nucleotide substitutions that result in the production of a different amino acid
What are synonymous substitutions?
Nucleotide substitutions that result in no amino acid change
What is a structural mutation?
Any changes to the function of a protein, either as a result of an amino acid substitution or a premature stop codon
What are regulatory mutations?
Even in the absence of structural changes to a gene, there can also be mutations that influence the expression of a gene.
What can regulatory mutations influence?
Timing
Location
Amount a gene is expressed
What form of selection are most genes under?
Purifying
Describe the macroevolutionary approach to determining the form of selection acting on substitution rates.
Infer sequence evolution for a specific gene across a phylogeny
Compare the rate of substitution in non-synonymous mutations (dN or Ka) to the rate of change in synonymous mutations (ds or Ks)
ω=d_N/d_s expresses the relative amount of change at non-synonymous (amino acid changing substitutions) to synonymous (silent/no change substitutions) nucleotide sites
What does ω = 1 indicate?
Non-synonymous and synonymous mutations occur at the same rate. Consistent with neutral evolution.
What does ω >1 indicate?
Non-synonymous substitutions occur more often than synonymous change; consistent with adaptive changes to protein structure (positive selection)
What does ω < 1 indicate?
Non-synonymous substitutions occur less often than synonymous changes consistent with evolution to prevent changes in protein structure (purifying selection)
What is the equation for Tajima’s D?
Tajima’s D=(π-θ)/σ
What does a value of 0 for Tajima’s D indicate?
Neutral evolution
What does a value greater than 0 for tajima’s D indicate?
Balancing selection – maintains more nucleotide diversity than expected under neutral evolution
