H.W. DUE FRIDAY:
Sex Linked Inheritance Practice Problems Do your best to complete the practice problems below related to sex-linked inheritance.
1. Colorblindness is a
sex-linked, recessive disorder. What are the probable offspring outcomes
from a father who is colorblind and a mother who is homozygous normal vision?
Show your work!
2. Hemophilia is caused by a
recessive allele on the X chromosome.
a. Draw a Punnett square that
shows how a mother whose blood clots normally can have a daughter with
hemophilia. Include the genotypic and phenotypic ratios.
b. What is the father's
genotype and phenotype?
c. Why is it extremely
uncommon for a female to have hemophilia?
3. Duchenne Muscular
Dystrophy is caused by a recessive allele located on the X chromosome.
a. Draw a Punnett square that
show how two unaffected people can have a child with muscular dystrophy.
Include the genotypic ratio and phenotypic ratio for the offspring.
b. Is the child with muscular
dystrophy male or female?
c. What is the probability
that the couple's next child will have muscular dystrophy?
d. What percentage of the
couple's male children will probably have muscular dystrophy?
e. What percentage of the
couple's female children will probably have muscular dystrophy?
4. Hypophosphatemia, a disorder that causes low
phosphate levels in the body and can cause bowed legs, is caused by a dominant
allele on the X chromosome.
a. Using A to represent the
allele for hypophosphatemia, draw a punnett square that shows the possible
offspring from a woman with genotype XAXa and a man with
genotype XAY.
b. What percentages of the
children have hypophosphatemia?
c. Are males more likely to
have the disorder than females? Explain.
d. Draw a Punnett square that
show the possible offspring of a woman with a normal phenotype and a man with
hypophosphatemia. Include the genotypic and phenotypic ratios for the
offspring.
e. What percentages of the
children have the disorder for this cross?
f. What percentages of the
male offspring have the disorder for this cross? Explain this result.
