Two Drosophila with blue eyes are mated and produce 973 flies with blue eyes and

Question

Two Drosophila with blue eyes are mated and produce 973 flies with blue eyes and 464 wild-type flies. Note: As described in your textbook, wild type Drosophila eye color is red. What is the genetic basis for these results?

a. simple dominance—the mutant allele is dominant to the wild-type allele

b. a recessive lethal allele

c. incomplete dominance—the mutant allele is partially dominant to the wild-type allele

d. X-linkage – the alleles for this trait are X-linked

e. simple gene interaction

f. pleiotropy

Explanation / Answer

Answer

Answer is b- a recessive lethal allele

Explanation:

Lethal allele:

A lethal allele is one that has the potential to cause the death of an organism. These alleles are typically the result of mutations in essential genes. They are usually inherited in a recessive manner.

Consider BL is normal blue colored and BI is lethal recessive genes.

Carrier female with blue colored eyes is BL BI and male with blue coloured eyes   is BL b

If we crossed a male blue eyed Drosophila with female blue eyed Drosophila (acts as a carrier of lethal allele), then the cross is as follows.

If we cross a carrier female BL BI with normal blue coloured male BL b

(Carrier female) BL BI                                    X                     BL b (Normal male)

Then the offspring’s obtained are

  BL BL                               BL b                             BL BI                                  BI b

Normal blue                   wild type red                  Normal blue                         Lethal dies

BI b is the lethal in this case

Finally we got the ratio 2:1 of blue eyed Drosophila (973 flies) with red colored wild type Drosophila (464flies).

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