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An Rh negative woman is married to an Rh positive man whose father was also Rh negative. What are the chances that their child will be affected?

Correct answer: B. 50%

  • A. 25%
  • B. 50%
  • C. 75%
  • D. 100%

Explanation

Given that that man's father was Rh-negative and man is Rh-positive,the man must be heterozygous for Rh-positive. Rh negative woman should be homozygous as recessive allele only expresses itself in homozygous condition. There is a fifty percent chance of being "affected" with Rh negative phenotype as shown:

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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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