A person was married to his cousin and both are heterozygous for Sickle Cell anemia. Among their four kids, what will be the proportion of homozygotes?
Correct answer: B. 50%
- A. 75%
- B. 50%
- C. 100%
- D. 25%
Explanation
As can be seen from the cross below, 50 percent of the offspring are heterozygotes, i.e. 50 percent possess the sickle cell trait. 25 percent are normal i.e. homozygous for HbN, while 25 percent have sickle cell anemia, i.e. homozygous for HbS. In total, 50 percent are homozygous (25 percent plus 25 percent) so, option B is correct.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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