Asked in FBISE Biology 2022 SLO — Paper 3 2022Moderate

If one pair of alleles exhibits complete dominance while the other pair exhibits incomplete dominance, what will be the outcome in F1 generation of a cross between AABB (Male) X aabb (female) parents?

Correct answer: D. there will be 100% recombinant phenotypes

  • A. all phenotypes will be similar to the male parent
  • B. all phenotypes will be similar to the female parent
  • C. there will be 1:1 between both parental phenotypes
  • D. there will be 100% recombinant phenotypes

Explanation

D) The correct answer is 100% recombinant frequency. This occurs because if one pair of alleles exhibits complete dominance (A and a) and the other pair exhibits incomplete dominance (B and b), the resulting offspring (F1 generation) will show traits that are a combination of the traits of the parents. Since there is no dominant-recessive relationship for the B and b alleles, both alleles will be expressed, resulting in a phenotype different from either parent. Therefore, all offspring will display a recombinant phenotype, indicating 100% recombinant frequency.

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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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