Population Genetics Flashcards
Average genetic difference between two random human beings
~1/1000 bp
or, about 99.9% the same
About what percentage of all variants are SNPs?
90%
The remaining 10% are either rarer, or are variants of a different sort – stretches of the DNA where there is either extra or missing DNA sequence
Average genetic difference between two random chimps
About ~1/300 bp
About 99.6% the same
This represents about 3 times the genetic diversity that humans have
Average genetic difference between a random human and a random chimp
~1/100 bp
About 99.0% the same
De Novo Human Mutation Rate
1.2 x 10-8 mutations per base pair per generation
or
1.2 de novo mutations per 108 bp per generation
Note: David Reich’s estimate is slightly larger, obtained using microsatellite data.
Mutation rate, gender, and age
Most new mutations come from the paternal line (~85% of all new mutations). Furthermore, the mutation rate increases with advancing paternal age. There may also be some variability between people in mutation rates, but this has not yet been thoroughly studied
Every human carries approximately ___ unique de novo mutations.
100 unique de novo mutations
Probability of neutral allele peristence
1 / 2N
Where N is a product of population size
The 1/2 is the coinflip regarding whether or not the de novo gene is passed on in reproduction.
N is a complicated function dealing with survival, reproduction rate, population size, etc.
Quantitative Human Genetic Drift
N = 10,000 because for most of human history, the human population size has been 10,000
Genetic drift is greater in . . .
a smaller population
Typically, deleterious mutations are ___ and ___.
Typically, deleterious mutations are rare and young.
Each person carries dozens or hundreds of loss of function alleles, but these mostly go unobserved because. . .
recessive embryonic lethal
Proportion vs Minor Allele Frequency for deleterious vs neutral mutations
Impacts of rapid expansion on the human genome
The impact of the expansion has been to increase the number of rare alleles compared with what would be expected under a constant sized population.
Linkage disequilibrium
How shared ancestry and recombination leads to different degrees of correlation amonge alleles.
Hardy-Weinberg Equilibrium
