The F2 phenotypic ratio of a dihybrid cross between two heterozygotes is
Correct answer: A. 9:3:3:1
- A. 9:3:3:1
- B. 3:1
- C. 1:1:1:1
- D. 12:3:1
Explanation
Each gene independently gives a three to one ratio, so combining two of them multiplies out to nine both dominant, three of each single dominant and one both recessive. The ratio holds only if the two genes assort independently, which requires them to be on different chromosomes. 1:1:1:1 is what a dihybrid test cross gives, and 12:3:1 arises when one gene masks another.
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About Mendel's Laws of Inheritance
Mendelian inheritance explains how alleles separate into gametes and assort during reproduction, producing predictable genotype and phenotype ratios. Questions cover dominance, recessiveness, homozygous and heterozygous conditions, the laws of segregation and independent assortment, monohybrid and dihybrid crosses, test crosses and the limits caused by linked genes.
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