University:
York University
Course:
BIOL 2040 | Genetics
Academic year:

2019
Views:

7

Pages:

3
Author:

Nick T.

CHAPTER 5 Gene linkage and recombination Synetic genes = Genes located on the same chromosome P bciba xb*c/b'c F₁ (all identical) bct/b'c Testcross ♀ bcib'c x ♂ bcib'c Testcross progeny 2934 b cibc (Parental classes) 2934 + 2768 = 77% 2768 b'c/bc 871 b'c/bc (Recombinant classes) 871 + 846 = 23% 846 bc/bc Total 7419 Recombination helps ensure proper chromosome segregation during meiosis I (a) Meioses with no crossing-over between A and B produce 4 parental gametes. (b) Meioses with one crossover between A and B produce 2 parental and 2 recombinant gametes. Genes are linked = less AB AB ab ab Meiosis I Meiosis II AB AB ab ab More frequent Less frequent Recomb Freq will not exceed 50%. → Meiosis w/o crossovers produce only parental Chromosomes. Linked Genes = RF<50% Unlinked genes = RF=50% → 2 genes are further away from crossover. Vg-b = (252+241+131+118) / 4197 x 100 = 17.7 1779 vg b pr - Parental combinations for all three genes 1654 vg+ b+ pr+ - Parental combinations for vg relative to pr 252 vg+ b pr+ - Recombinants for vg relative to pr 241 vg b+ pr+ - Recombinants for b relative to vg and pr 131 vg b pr+ - Recombinants for b relative to vg 118 vg b+ pr - Recombinants for pr relative to vg and pr 13 vg b pr+ - Recombinants for pr relative to vg and b 9 vg+ b+ pr - Recombinants for pr relative to vg and b Vg-Pr = (252+241+13+9) / 4197 x 100 = b-pr = (131+118+13+9) / 4197 x 100 = Chromosomal interference - Occurrence of crossover in one portion of a chromosome interferes with CO in an adjacent part of the chromosome.. Null Hypothesis - observed values are no different from expected values. χ² = Σ((O-E)² / E) → chi-square Model organisms: All 4 haploid products of each meiosis are contained