Class Notes (809,487)
Canada (493,752)
Biology (6,677)
Biology 1001A (1,723)
Lecture 13

Biology 1001A Lecture 13.pdf

2 Pages
Unlock Document

Western University
Biology 1001A
Beth Mac Dougall- Shackleton

Biology 1001A | 2012 LECTURE NOTES Lecture 13 Selection & Fitness –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– - just because an allele is recessive to another allele, this does not automatically decrease the occurrence of the allele, therefore it will not simply die out - evolution is a change in allele frequencies from one generation to another Hardy-Weinberg Principle - in a large, random-mating population, where mutations are rare enough to be ignored, in the absence of immigration or emigration, and if there is no selection... - then we can use the allele frequencies to calculate genotype frequencies ▯ f(A1A 1 = p ▯ ▯ f(A1A 2 = 2pq▯f(A2A 2 = q2 1. Use observed phenotype or genotype frequencies to calculate allele frequencies 2. Use product rule to calculate expected genotype frequencies (under HWE) 3. Compare observed vs expected genotype frequencies: is the population in HWE? Hardy-Weinberg is a “null model” - to recognize evolution ,we need to know what a non-evolving population looks like - if genotype frequencies can be predicted from allele frequencies, population is in Hardy-Weinberg Equilibrium (HWE) and this locus - allele frequencies will not change while this is true - if not, one or more assumptions of HWE are violated, therefore the population may be evolving Selection: Not all genotypes have equal fitness - if selection pressure is strong, evolution proceeds more quickly Fitness & the Strength of Selection - for each genotype we can estimate (based on lifetime reproductive success, survival...) its - average absolute fitness (W) - average relative fitness (w) - by definition, fittest genotype(s) has w = 1 - all others w = W / Wmax - difference in w between genotypes reflects strength of selection - we are more interested
More Less

Related notes for Biology 1001A

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.