Which one of the following cannot be explained on the basis of Mendel's law of dominance?
Correct answer: C. Alleles do not show any blending and both the characters recover as such in F2 generation.
- A. The discrete unit controlling a particular character is called a factor.
- B. Out of one pair of factors one is dominant, and the other recessive.
- C. Alleles do not show any blending and both the characters recover as such in F2 generation.
- D. Factors occur in pairs
Explanation
According to Mendel's law of dominance, in heterozygous individuals, a character is represented by two contrasting factors called alleles or allelomorphs which occur in pairs. Out of the two contrasting alleles, only one is able to express its effect in the individual. It is called the dominant factor or dominant allele. The other allele which does not show its effect in the heterozygous individual is called recessive factor or recessive allele. Option (c) in the given question cannot be explained on the basis of law of dominance. It can only be explained on the basis of Mendel's law of independent assortment, according to which in a dihybrid cross, the two alleles of each character assort independently (do not show any blending) of the alleles of other character and separate at the time of gamete formation. Both the characters are recovered as such in the F2 generation producing both parental and new combinations of traits.
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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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