Hemophilia is a sex-linked, recessive genetic disorder. If a male with hemophilia and a homozygous normal female have a female child, what is the probability that the girl will be a carrier for hemophilia?

Responses

0%
0%

25%
25%

50%
50%

100%

1 answer

Hemophilia is a sex-linked recessive disorder commonly carried on the X chromosome. In this case, we have:

  • The male with hemophilia has the genotype \( X^hY \) (where \( X^h \) represents the X chromosome carrying the hemophilia allele and \( Y \) represents the Y chromosome).
  • The homozygous normal female has the genotype \( X^X \) (where both X chromosomes are normal).

To find the probability that their female child will be a carrier, we can construct a Punnett square. The possible gametes contributed by each parent are:

  • Male with hemophilia: \( X^h \) or \( Y \)
  • Homozygous normal female: \( X \) or \( X \) (both gametes are the same)

Now, create a Punnett square:

\[ \begin{array}{c|c|c} & X & X \ \hline X^h & X^hX & X^hX \ \hline Y & XY & XY \ \end{array} \]

The potential offspring from this cross would be:

  1. \( X^hX \) (female, carrier)
  2. \( X^hX \) (female, carrier)
  3. \( XY \) (male, normal)
  4. \( XY \) (male, normal)

Out of the four possible combinations, the two female offspring (\( X^hX \)) are carriers of hemophilia.

Thus, the probability that the female child will be a carrier for hemophilia is 100%.

The correct answer is 100%.