Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

1. Heritable

Explanation:

Mutations are defined as changes in chemical structure of gene at the molecular level. Since genes are the unit of heredity, mutations in genes are passed from one generation to next, exception is lethal mutation; option A is correct and B is incorrect. Owing to genetic code redundancy and diploidy, some mutations are neutral. As we know that wobble base pairing allows multiple codons, most of which differ in their base, to code for single amino acid. For example, serine is encoded by UCC, UCA, UCG, AGU, and AGC. Therefore, any mutation that changes the last letter of the codon of serine will have no effect. Diploids have two copies of a gene, the presence of one functional copy is sufficient to ignore the effects of the mutation in the second copy. Some mutation is deleterious and provides the raw material for natural selection to act upon and thus causing evolution; option D is correct. Only a few mutations are beneficial that impart survival or reproductive advantage; for example ability of milk digestion in human kids, option C is incorrect.