With population

With population - heterozygotes mutation will introduce new...

This preview shows page 1. Sign up to view the full content.

With population bottlenecks where the population size drops to a small number in one generation, the effective population size is not just the average of N's for each generation. To estimate the Ne, one calculates the harmonic mean population size as follows: 1/Ne = 1/t_1/Nt where t = the number of generations and Nt = the population size at each generation. Thus with population sizes of 100, 100, 20, 100 the arithmetic mean = 80 but 1/Ne = 1/4(1/100 + 1/100 + 1/20 + 1/100) = 1/4(0.08) = 0.02, so Ne = 1/0.02 = 50 . Thus the smaller population size has a disproportionate effect on the effective population size. This is a very important issue in conservation efforts concerning endangered species. DRIFT AND MUTATION Drift will tend to reduce heterozygosity (for our purposes this equals the proportion of
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: heterozygotes), mutation will introduce new alleles which will serve to increase heterozygosity. This provides yet another example of a "fight" between opposing evolutionary forces. When the mutation rate is close to the reciprocal of the population size , heterozygostity will be high (i.e., a considerable amount of variation will exist in the population). The "balance" of this equilibrium can be described by an equation for the equilibrium frequency of heterozygotes: H Å Plug in Ne's and u's to determine balance: when Ne = 1/u, H = 0.8; when u>1/Ne then heterozygosity will be higher; when u<1/Ne heterozygosity will be lower....
View Full Document

{[ snackBarMessage ]}

What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern