Moderate

If a cross follows Mendel's law of independent assortment, it results in phenotypic ratio:

Correct answer: C. 9 : 3 : 3 : 1

  • A. 3 : 1
  • B. 1 : 2 : 1
  • C. 9 : 3 : 3 : 1
  • D. 9 : 3 : 2 : 1

Explanation

This 9:3:3:1 phenotypic ratio is the classic Mendelian ratio for a dihybrid cross in which the alleles of two different genes assort independently into gametes. Figure 1: A classic Mendelian example of independent assortment: the 9:3:3:1 phenotypic ratio associated with a dihybrid cross (BbEe × BbEe).

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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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