6. In Cross 1, a yellow eyed, long wing fruit fly from a pure breeding strain is
ID: 98804 • Letter: 6
Question
6. In Cross 1, a yellow eyed, long wing fruit fly from a pure breeding strain is mated to a red eye, short wing fruit fly from a pure breeding strain. All of their offspring (F1) had red eyes and long wings. In Cross 2, one of the F1 offspring is mated to a fly with yellow eyes and short wings, and this cross gave the following F2 population: 194 flies with long wings and red eyes, 796 flies with yellow eyes and long wings, 206 flies with yellow eyes and short wings, and 804 flies with red eyes and short wings. a. Assign gene names and allele names and abbreviations for each b. Write the genotypes of the two parents in Cross 1 c. Write the genotype of the F1 offspring and the fly that it mates to (Cross 2) d. Which allele of each gene is dominant and which is recessive? e. What gamete genotypes would you expect from the red/long parent in Cross 2 if the genes involved were assorting independently (i.e. as if they were on different chromosomes)? f. What ratio would you expect to find in the progeny of Cross 2 if the genes involved were assorting independently? Draw a Punnett square to support your answer.Explanation / Answer
Solution) As wee see in the first case that the two parents are pure breeding which means they are heterozygous. so, all the F1 progenies would be heterozygous and the dominant gene will be expressing its phenotype. therefore, Red eye color is dominant to yellow eye color and long wings are dominant to short wings.
a) Let's say "R" be the dominant allele for red eye color and "r" be the recessive allele for yellow eye color. similarly, "L" be the dominant allele for long wing and "l" be the recessive allele for the short wings.
b) genotypes of the two parents in cross 1 would be; P1 x P2; yellow eyes long wings x red eyes short wings
P1 x P2: rrLL x RRll
c) Genotype of the F1 would be RrLl (Red eyes and long wings) and the parent 3 (which it mates with) would be rrll (yellow eyes and short wings)
d) "R" be the dominant allele for red eye color and "r" be the recessive allele for yellow eye color. similarly, "L" be the dominant allele for long wing and "l" be the recessive allele for the short wings.
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