Mrs. Eryth is carrier of the sex-linked hemophilia allele, and Mr.
Eryth is normal (as far as blood chemistry goes).
A. Draw a Punnet square that shows the theoretical genotypes and
phenotypes among their children.
B. They actually have 4 male and 4 female children; how many of
each sex would be expected to be hemophiliacs, carriers, and
normal?
A. Alright, let's get those Punnett squares rolling! Since Mrs. Eryth is a carrier of the sex-linked hemophilia allele (let's represent it as h), and Mr. Eryth is normal (let's represent it as H), we can set up the Punnett square as follows:
| H | h |
________________________
H | HH | Hh |
________________________
h | Hh | hh |
So, the genotypes and phenotypes of their potential children are as follows:
- 25% chance of being HH and having normal blood chemistry
- 25% chance of being Hh and also having normal blood chemistry (carriers)
- 25% chance of being Hh and being a hemophiliac
- 25% chance of being hh and being a hemophiliac
B. Now, if they actually have 4 male and 4 female children, we can expect the following distribution among the sexes for hemophiliacs, carriers, and normal individuals:
- Hemophiliacs: Since hemophilia is a sex-linked disorder, it typically affects males more often than females. As per the Punnett square, the chances of having a male hemophiliac child are 25%, so we can expect 1 out of their 4 male children to be hemophiliacs.
- Carriers: Again, referring to the Punnett square probabilities, the chances of having a carrier child (male or female) are 50% (25% Hh and 25% Hh). So, we can expect 2 out of their 4 male children and 2 out of their 4 female children to be carriers.
- Normal: The chances of having a normal child (male or female) are 25% (HH genotype). So, we can expect 1 out of their 4 male children and 1 out of their 4 female children to have normal blood chemistry.
Remember, these are just expected probabilities based on the Punnett square. Actual outcomes may sometimes bring surprises because genetics likes to play its own clownish games!
A. To determine the theoretical genotypes and phenotypes among their children, we first need to identify the genotypes of Mrs. Eryth and Mr. Eryth.
Mrs. Eryth is a carrier of the sex-linked hemophilia allele, so she heterozygous for the gene (X^hX). Mr. Eryth is normal, which means he does not carry the hemophilia allele (XY).
The Punnett Square can be set up as follows, with the gametes from Mrs. Eryth on the top and Mr. Eryth on the side:
X^h X
------------------
Y | X^hY XY
------------------
Y | X^hY XY
The possible genotypes of their children are: X^hX^h (hemophiliac female), X^hY (normal male), and X^hX (carrier female).
B. Since Mrs. Eryth is a carrier, she has one X^h allele and one normal X allele. There is a 50% chance that each child she produces will inherit the X^h allele.
Out of the 4 female children, half would be expected to inherit the X^h allele and be carriers (X^hX) for hemophilia, and the other half would be expected to inherit the normal X allele (XX) and be normal.
Therefore, 2 out of the 4 female children would be carriers and 2 would be normal.
For the 4 male children, since the hemophilia allele is sex-linked, they would need to receive the X^h allele from Mrs. Eryth to be affected. However, since the father is normal (XY), none of the male children would inherit the hemophilia allele.
Therefore, none of the male children would be hemophiliacs, 4 would be normal, and all would be carriers.
To summarize:
- Out of the 4 female children, 2 would be carriers, and 2 would be normal.
- None of the male children would be hemophiliacs, all would be carriers, and all would be normal.
To answer this question, we need to understand the inheritance pattern for the sex-linked hemophilia allele. Hemophilia is a sex-linked recessive disorder that is carried on the X chromosome.
A. Punnett Square:
Let's represent the alleles for hemophilia using "Xh" for the hemophilia allele and "X" for the normal allele. Since Mrs. Eryth is a carrier of the hemophilia allele, her genotype will be "XhX", and Mr. Eryth's genotype will be "XY".
The Punnett square for their children would look like this:
Xh X
Y XhX XY
Y XhX XY
In this Punnett square, the top row represents the possible genotypes of the offspring and the first column represents the possible genotypes of the father.
B. Hemophilia in their children:
Since hemophilia is a sex-linked recessive disorder, the presence of the hemophilia allele on the X chromosome results in the expression of the disorder. Let's analyze the possibilities for each child:
1. Female children (XX):
- Hemophiliacs (XhXh): Since Mrs. Eryth is a carrier and has the Xh allele, there's a possibility that her female children will inherit the Xh allele from her and become hemophiliacs. However, since the father does not have the hemophilia allele, none of the female children will be hemophiliacs.
- Carriers (XhX): There's a 50% chance that the female children will inherit the Xh allele from Mrs. Eryth and become carriers, as one X chromosome will always come from the mother.
- Normal (XX): There's a 50% chance that the female children will inherit the normal X allele from Mrs. Eryth and be completely normal.
2. Male children (XY):
- Hemophiliacs (XhY): Since hemophilia is carried on the X chromosome, a male child needs to inherit the Xh allele from Mrs. Eryth in order to be hemophiliac. Thus, there's a 50% chance that male children will inherit the Xh allele and become hemophiliacs.
- Carriers (XhY): There's a 50% chance that the male children will inherit the Xh allele from Mrs. Eryth and become carriers, as they will always inherit the Y chromosome from the father.
- Normal (XY): There's a 50% chance that the male children will inherit the normal X allele from Mrs. Eryth and be completely normal.
So, out of their 8 children (4 males and 4 females), we can expect the following distribution:
- Hemophiliacs: 1 male child (XhY)
- Carriers: 3 female children (XhX)
1 male child (XhY)
- Normal: 3 female children (XX)
3 male children (XY)