A gene for eye colour in Drosophila occurs on the X chromosome. The allele for red eyes, XR, is dominant over the allele for white eyes, Xr.
A heterozygous red-eyed female fruit fly was crossed with a white-eyed male fruit fly. Complete the following Punnett square for this cross.
Answer
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Answer
Answer
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Y Answer
Answer
options - XR, Xr - XXRR, XXRr, XXrr
options for Y - XRY, Xry
2.
Use the following information to answer the next two questions.
Hemophilia is an X-linked disorder that affects the body’s ability to create blood clots. The allele for normal blood clotting, XH, is dominant over the allele for hemophilia, Xh.
An unaffected female that is not a carrier mated with an affected male. Which of the following rows identifies the possible genotypes of the offspring?
a.
Female Male
XHXh XHY and XhY
b.
Female Male
XHXH and XHXh XHY
c.
Female Male
XHXH and XHXh XHY and XhY
d.
Female Male
XHXh XHY
3. An unaffected daughter from the above cross married a man who does not have hemophilia.
Determine the probability of their offspring being
A daughter with hemophilia
A daughter without hemophilia
A son with hemophilia
A son without hemophilia
Express your answer as a phenotypic ratio.
Number:
Answer
Answer
Answer
Answer
Phenotype:
Affected
female
Unaffected
female
Affected
male
Unaffected
male
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