A researcher is interested in a novel gene in drosophila called “COVID” which causes the flies to become antisocial and maintain a large distance from other flies. She performs two “reciprocal crosses” to determine the possible genetics of this gene. First, she crosses a true-breeding COVID female to a true-breeding wild-type male and produces the following progeny: All of the female progeny are wild-type and all of the male progeny from this cross are COVID. Next, she does a reciprocal cross and mates a true-breeding male COVID fly to a true-breeding female wild-type and generates the following progeny: All flies are wild-type. What is a possible explanation for our researcher’s results?
Group of answer choices
COVID is autosomal recessive.
COVID is sex-linked dominant.
COVID is autosomal dominant with incomplete penetrance.
COVID is sex-linked recessive.
d) COVID is sex-linked recessive.
let the alleles be Xc- COVID phenotype, XC- normal flies
genotype of the true breeding COVID females is XcXc and genotype of normal males is XCY
XCY * XcXc
XC | Y | |
Xc | XCXc ( wildtype female) | XcY ( COVID male) |
Xc | XCXc ( wildtype female) | XcY ( COVID male) |
all female progenies are wildtype and all males shows COVID phenotype.
Now let`s do reciprocal cross
wildtype female * COVID male
XCXC * XcY
XC | XC | |
Xc | XCXc ( normal female) | XCXc ( normal female) |
Y | XCY ( normal male) | XCY ( normal male) |
all progenies are normal.
so the mode of inheritance of COVID is Sex-linked recessive.
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