Read the following statements and pick the incorrect statement.

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Differences among individuals of the same species are termed as variations.

Recessive phenotype is due to the absence of a dominant gene.

Allelic pairs at a locus control the same character, but need not always control the same trait.

Recessive genes could be unmodified genes, but the dominant gene is always a modified gene.

answer is D.

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Detailed Solution

The normal allele produces the normal enzyme that is needed for the transformation of a substrate S. Theoretically, the modified allele could be responsible for production of –

(i) the normal/less efficient enzyme, or (ii) a non-functional enzyme, or (iii) no enzyme at all.

The modified allele is equivalent to the unmodified allele, i.e., it will produce the same phenotype/trait, i.e., result in the transformation of substrate S. Such equivalent allele pairs are very common.

But, if the allele produces a non-functional enzyme or no enzyme, the phenotype may be effected. The phenotype/trait will only be dependent on the functioning of the unmodified allele.

The unmodified (functioning) allele, which represents the original phenotype is the dominant allele and the modified allele is generally the recessive allele. Hence, in the example above the recessive trait is seen due to non-functional enzyme or because no enzyme is produced.

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