Topic 7

• any heritable change in DNA sequence, or DNA compliment (e.g. # of chromosomes) • ultimate source of all variation w/in pop’ns

• mut’ns in somatic cells that are not heritable - no evolutionary consequence

-occur in gametes or the cells that produce them and can be passed on to offspring

changes in the number or structure of chromosomes • inversions: goes from one strand to the other strand (and also rotates 180 degrees) • point mutations: a) transitions b) transversion

goes from one strand to the other strand (and also rotates 180 degrees)

change of a single nucleotide in a DNA sequence a) Replacement mut’ns (Non-synonymous): mut’ns that change the a.a. in a protein sequence b) Silent mut’ns (synonymous): do not change the a.a.

substitution of a purine with a purine or a pyrimidine with a pyrimidine -much more common than transversions

substitution of a purine with a pyrimidine and vice versa

• additions or deletions - in coding regions: can be highly deleterious –> can disrupt the reading frame

• often, genes or groups of genes can duplicate • important mode of duplication • e.g. major histo-compatibility complex (arisen by duplication)

• A–>a = u (forward mut’n rate) 2. a–>A = v (back mut’n rate)

• assumes each new mutation creates a new unique allele - by def’n, all copies of any given allele will be IBD

• length of alleles incrementally increases or decreases one repeat at a time via mutation • gain or lose repeats

mutations which result in lowered fitness

-selection that acts to remove or lower the frequency of a deleterious mutation

• continued mutation: keeps pumping it back in • dominance effects: e.g. Aa–>hides in heterozygotes • genetic drift: when pop’n size is very small

have no effect of fitness • e.g. silent mutations which do not change an a.a. are typically neutral • note: silent mutations are not always neutral

have very little effect on fitness (so little that they are effectively neutral)

• increases the fitness • they are rare in comparison to deleterious and neutral mutations • positive selection: sel’n that increases the frequency of advantageous mutations –> reuslts in adaptive evolution

• caused by mutation selection balance (ignoring drift) • results in deleterious effects • load is equivalent to the reductions in the relative pop’n fitness • basically deleterious alleles hide in heterozygotes

• does not affect H-W eq’m - next gen, you have H-W eq’m..but based on the new allele freq’s