Erythroblastosis foetalis is caused when fertilization takes place between gametes of:
Correct answer: A. Rh ̄ female and Rh+ male
- A. Rh ̄ female and Rh+ male
- B. Rh+ female and Rh ̄ male
- C. Rh+ female and Rh+ male
- D. Rh ̄ female and Rh ̄ male
Explanation
Erythroblastosis fetalis is caused by Rh incompatibility when an Rh-negative mother is exposed to Rh-positive fetal blood, leading to an immune response. This occurs in Option A, where an Rh-negative female and an Rh-positive male can produce an Rh-positive offspring. The mother's immune system can attack the fetal red blood cells in subsequent pregnancies. Options B, C, and D do not lead to erythroblastosis fetalis because there is no Rh incompatibility: in Option B, the mother is Rh-positive and can tolerate Rh-negative blood; in Option C, both parents are Rh-positive; and in Option D, both are Rh-negative, eliminating any Rh factor conflict.
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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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