solution to question C pls Diagnostic Problem 3 Make sure th

solution to question C pls

Diagnostic Problem 3 Make sure that you show your work for the following problems. You are given two blue beetles and two black beetles. a) Cross 1: You mate (or cross) blue beetle #1 to black beetle #1 and obtain 220 black beetles in the F1 generation, What is the dominant phenotype? What is the recessive phenotype? What are the genotypes of the two parents and the offspring? Be sure to indicate which allele is associated with the dominant phenotype. b) Cross 2: You mate blue beetle #2 to black beetle #2 and obtain 55 blue beetles and 65 black beetles. What are the genotypes of the two parents and the offspring? c Cross 3: You mate two black offspring produced in Cross 2. What are the possible genotypes and phenotypes of the offspring? What are the expected proportions of these genotypes and phenotypes?

Solution

Please find the answers below:

According to the information, the cross between blue and black beetle yeilds all black beetles in F1 generation. This means that black phenotype is dominant over blue. Further, since all the beetles are black in color, they should be all heterozygous/homozyous in nature. However, they cannot be homozyous in nature because in that case a gene for black color must be obtained from other parent which would make it black. Thus, the genotypes must be homozygous for both the parents i.e.:

Blue beetle : bb

Black beetle: BB

Thus, the offsprings will have:

Phenotype: All black

Genotype: All Bb

Part b: Thus, for part b of the question it can be seen that there has been conducted a cross where blue and black beetles have been crossed to yield an almost 1:1 ratio of both beetles. This suggests that this is a test cross where the F1 individual or Bb has been crossed with homozygous recessive individual from parent generation i.e. bb.

Part C: As it can be seen in part b, the genotype of black beetle is Bb and blue beetle is bb. Thus, the cross would be:

Genotype: bb: Bb :: 1:1

Phenotype: Blue : black :: 1:1

	B	b
b	Bb	bb
b	Bb	bb