The following couples plan to marry and want to know the chance of having a chil
ID: 258982 • Letter: T
Question
The following couples plan to marry and want to know the chance of having a child with the following diseases. You are a genetic counselor who needs to answer their questions. Write out the genotypes of the crosses and perform a Punnett square to determine the probability of the child inheriting the disease.
a. an affected father and carrier mother for color blindness (X-linked recessive)
b. an unaffected father and a carrier mother for hemophilia (X-linked recessive)
c. an unaffected father and an unaffected mother for color blindness
d. an affected father and an unaffected mother for color blindness
Explanation / Answer
a) Genotype of affected father for color blindness - XcY.
Genotype of carrier mother for color blindness - X+Xc.
Cross between them XcY X X+Xc.
Gametes formed Xc and Y X+ and Xc
Next generation
The probability of the child inheriting the disease - 1/2 .
b) an unaffected father and a carrier mother for hemophilia.
Genotype of unaffected father for hemophilia - XY.
Genotype of carrier mother for hemophilia - XhX.
Cross between them XY X XhX
Gametes formed X and Y Xh and X.
Next generation
The probability of the child inheriting this disease - 1/4.
c) an unaffected father and an unaffected mother for color blindness.
Genotype of unaffected father for color blindness - XY.
Genotype of unaffected mother for color blindness - XX.
All are unaffected, then the probability of the child inheriting this disease - zero 0%.
d) an affected father and an unaffected mother for color blindness.
Genotype of affected father for color blindness - XcY.
Genotype of unaffected mother for color blindness - XX.
Cross between them XcY X XX
Gametes formed Xc and Y X and X.
Next generation
Male/Female X+ Xc Xc X+Xc(unaffected carrier female) XcXc(colorblind female) Y X+Y(unaffected male) XcY(colorblind male)Related Questions
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