Ch3: Hardy Weinberg Flashcards
Define what a diploid is
Species that have 2 copies of each chromosome and therefore, 2 alleles per 1 gene
Define incomplete dominance
What there is no dominant/recessive relationship in heterozygotes, and thus heterozygotes have intermediate phenotypes (a mix of the 2 not showing both individually - codominance)
What are the Mendelian Ratios, and the ratio of the monohybrid cross:
Mendelian Ratios: Bb x Bb
= 1 : 2 : 1 (BB : Bb: bb)
Monohybrid Cross: BB x bb
= 3 : 1 (BB : bb)
What is the equation for ALLELE frequencies?
p + q = 1
Where p = B and q = b
What is the equation for GENOTYPE frequencies? And how can we mathematically derive this equation?
p^2 + 2pq + q^1 = 1
(p + q)^2 = 1^2 = 1
p^2 = B x B
q^2 = b x b
2pq = B x b/ b x B
How do we derive Allele frequencies from genotype frequencies?
p(B) = fB/B + 1/2 fB/b
q(b) = fb/b + 1/2 fB/b
What does Hardy Weinberg Equilibria (HWE) show?
See Doc, 3a:
that the allele frequencies will NOT change from 1 generation to the next;
- hence no change in genotype frequencies
- NO dominant allele overruns frequency
Is variation created or destroyed when genes are transmitted from 1 generation to the next in HWE?
No, variation is not created nor destroyed when genes are transmitted from 1 generation to the next in HWE;
- it is impossible for dominant phenotypes to overrun recessive phenotypes as allele frequencies don’t change
Do HWE allele frequencies change over time?
frequency distribution will not change from generation to generation once a population is in Hardy-Weinberg equilibrium
- and NO evolution occurs under HWE
What are the assumptions/conditions of HWE (hint there are 5)
1) No gene flow (migration - emigration or immigration)
2) no mutation (no new alleles)
3) infinite population size (to reduce the impact of gene drift as drift impacts large population less than smaller populations)
4) Mating is random
5) All organisms are of equal fitness (NO selection)
Hence what does HWE demonstate?
that frequencies of alleles will NOT change in the absence of outside forces
Equation for degrees of freedom
n - 1, where n is the number of alleles tested (number of variables tested)
If, after a Chi^2 test, p<0.05 do we accept the null hypothesis?
What does this mean for HWE?
If p<0.05 we reject the null hypothesis as results are significant.
- if we reject the null hypothesis we also reject HWE, because the variable we tested has a significant impact on the results we got, and hence HWE assumptions are broken (other factors working on population)
