The correct answer is Option (2) → (B) and (C) only
Explanation of the Statements:
(A) During incomplete dominance, the modified allele is the dominant allele
- Incorrect: In incomplete dominance, neither allele is completely dominant. Instead, the heterozygote shows an intermediate phenotype between the two parental traits. There is no "modified dominant allele" in this case.
(B) In polygenic inheritance, the effect of each allele is additive
- Correct: Polygenic inheritance involves the influence of multiple genes on a single phenotypic trait. Polygenic inheritance is an inheritance pattern controlled by three or more genes (multiple genes) and the graded phenotypes are due to the additive or cumulative effect of all the different genes of the trait. An example of human skin colour to understand the phenomenon of polygenic inheritance.
(C) A gene is called pleiotropic when it exhibits multiple phenotypic expressions
- Correct: The term pleiotropy is derived from the Greek words pleio, which means "many," and tropic, which means "affecting." When a single gene can exhibit multiple phenotypic expression. Such a gene is called a pleiotropic gene. An example of this is the disease phenylketonuria, which occurs in humans.
(D) Mutation means alteration of DNA sequence which ensures change only in the phenotype of an organism
- Incorrect: While mutations are alterations in the DNA sequence, they do not always ensure a change in phenotype. Some mutations are silent and do not affect the phenotype due to redundancy in the genetic code.
Conclusion:
The statements (B) and (C) are correct, making the answer (B) and (C) only.
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