The woman who is a heterozygote and has sickle cell trait makes two possible gametes. One contains the normal hemoglobin-producing allele (H) and the other contains the sickle cell allele (h). The probability of producing either type of egg cell is 1/2.
The male who is homozygous for sickle cell anemia produces only sperm cells containing the sickle cell allele (h). The probability of sperm cells containing the sickle cell allele is 1.
When multiplied,...
The woman who is a heterozygote and has sickle cell trait makes two possible gametes. One contains the normal hemoglobin-producing allele (H) and the other contains the sickle cell allele (h). The probability of producing either type of egg cell is 1/2.
The male who is homozygous for sickle cell anemia produces only sperm cells containing the sickle cell allele (h). The probability of sperm cells containing the sickle cell allele is 1.
When multiplied, the probability of an egg with the normal hemoglobin allele and a sperm with the sickle cell allele forming the zygote is 1/2 X 1 which equals 1/2.
When multiplied, the probability of an egg with the sickle allele joining with a sperm with the sickle cell allele at fertilization is 1/2 x 1 or 1/2.
Therefore, it is a fifty-fifty chance of having a child with sickle cell trait (Hh) or a child with sickle cell anemia (hh) as a result of random fertilization with this couple's gametes.
If you look at the link I provided, problem three shows a parent who has sickle cell and a parent with has sickle cell trait producing offspring. Although the problem has the father as a heterozygote and the mother has the disease, the results will still be the same as I described -- a fifty-fifty chance of offpsring with a homozygous disease phenotype (sickle cell anemia) or heterozygous (sickle cell trait).
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