BIOL1001 Lecture Notes - Lecture 15: Zygosity, Meiosis, Chromosome
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Mappi(cid:374)g the ge(cid:374)o(cid:373)e: organisms have many more genes than chromosomes many genes reside on each. Represented as: (cid:3002)(cid:3003)(cid:3028)(cid:3029) where the alleles of one homologue are together: crossing over = the process where genes are exchanged between paternal and maternal chromosomes during meiosis. Testing for independent assortment: to test = testcross a double heterozygote (aabb) with a double recessive homozygote (aabb) The four possible gamete combinations from meiosis = ab, ab, ab and ab in 1:1:1:1. Deviations from this ratio indicate that independent assortment has not occurred ratio (cid:894)fro(cid:373) me(cid:374)dle"s pri(cid:374)ciple of i(cid:374)depe(cid:374)de(cid:374)t assort(cid:373)e(cid:374)t(cid:895) The four possible genotypes of the progeny = aabb, aabb, aabb and aabb in. Wild-type (wwcrcr) = red eyes, straight bristles. Mutant (wwcrcr) = white eyes, crooked bristles. Testcross between mutant and wild to test for linkage: due to linked genes. However: progeny ratio does not follow 1:1:1:1 due to linked genes.