The homozygous gray (A) fly, the Drosophila fly with normal wings (B), was crossed with black (a) with the rudimentary wings (b) male. From crossbreeding, numerous offspring were obtained. Genes of these traits are linked and inherited together. Identify the genotypes and phenotypes F1 and F2. How would splitting occur if the signs were not linked?
1) In F1, all descendants are gray and with normal wings AaBb.
2) Since the genes are linked, two varieties of gametes AB and ab are formed in F1 hybrids.
3) Therefore, in F2, the splitting will be according to genotype 1AABB: 2AaBb: 1aabb, and according to the phenotype, 75% of the offspring are gray with normal fly wings and 25% are black with embryonic wings.
4) With unlinked inheritance, splitting would occur in accordance with Mendel’s third law on independent inheritance of characters in a ratio of 9: 3: 3: 1, since in this case two individuals cross
with genotypes AaBb.
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