I'm making my through this test, and I came across this question:
Hemophilia is an inherited bleeding disorder where blood does not clot properly. This disorder is caused by a recessive allele on the X chromosome. A couple has just learned that their daughter has hemophilia. They already have a son who does not have the disease. What are the genotypes of the couple and the two siblings? Explain your reasoning.
Could anyone explain what it means by genotype? I know a genotype is the genetic makeup of an organism, so I don't quite understand what it's asking.
son not hemophiliac ... X chromosome undamaged
... inherited undamaged X from mother and Y from father
daughter hemophiliac ... both x chromosomes damaged
... inherited damaged x from mother and father
father is hemophiliac
... has damaged x chromosome
... genotype ... xY
mother is "carrier"... not hemophiliac
... has one normal X and one damaged x
... genotype ... Xx
the mother is not hemophiliac
... her phenotype is "normal"
... her genotype could be XX or Xx ... at least one undamaged X
... she carries a recessive ... because her daughter is hemophiliac
... so her genotype is Xx
because hemophilia is a sex-linked recessive
... the daughter has a damaged x from each parent
wow gg
thx you
Wow Tysm Rscott you helped me understand this whole subject
In genetics, the genotype refers to the specific combination of alleles (variations of a gene) that an individual possesses. So, when the question asks for the genotypes of the couple and the two siblings, it is asking for the genetic makeup of each individual with respect to the alleles related to hemophilia.
To understand the genotypes in this scenario, it's important to know a few key points:
1. Hemophilia is caused by a recessive allele on the X chromosome. This means that an individual must inherit the hemophilia allele from both parents to have the disorder.
2. Since the son does not have hemophilia, it suggests that he has at least one dominant allele for clotting on his X chromosome.
Now let's consider the genotypes of the couple and the two siblings:
1. Daughter with hemophilia: Since the daughter has hemophilia, she must have inherited the recessive hemophilia allele from both parents. Therefore, her genotype would be 'XhXh', where 'Xh' represents the hemophilia allele.
2. Son without hemophilia: Since the son does not have hemophilia, he must have inherited a dominant clotting allele on either one of his X chromosomes. Since the couple already has a daughter with hemophilia, it suggests that the mother must be a carrier of the hemophilia allele ('XhX'). Therefore, the son's genotype would be 'XhY', where 'Y' represents the male-specific Y chromosome.
3. Genotypes of the couple:
Since the couple has a daughter with hemophilia and their son does not have the disorder, it suggests that the father is unaffected by hemophilia and does not carry the hemophilia allele ('XHY'). The mother is a carrier of the hemophilia allele ('XhX'). Therefore, the genotypes of the couple would be 'XHY' for the father and 'XhX' for the mother.
In summary, the genotypes of the couple and the two siblings are:
- Father: XHY
- Mother: XhX
- Daughter with hemophilia: XhXh
- Son without hemophilia: XhY