Question

4(a)(i) Explain briefly what is meant by independent assortment of genes. (ii) Give the reason blood group O in humans can only exist in homozygous form while blood groups A and B can exist in both homozygous and heterozygous forms. (b) Complete the table below by naming the classes of vertebrates in their evolutionary trends and giving one example each of the classes.

Accepted Answer

(a)(i) Independent assortment of genes refers to the fact that a gamete receives for one gene does not influence the allele received for another gene. Mendel's law of independent assortment states that the alleles of two or more different genes get sorted into gametes independently of one another.
(ii) Generally speaking, a trait that can only be expressed in the homozygous form is said to be recessive. Blood group O is recessive to A and B. Thus, AO leads to Heterozygous A, AA leads to Homozygous A, BO leads to Heterozygous B, BB leads to Homozygous B. If O is combined with either A or B, O will not be phenotypically expressed since O is recessive; only OO can be phenotypically expressed as O.
(b) Class of vertebrate and example: Pisces (fishes) - Tilapia, Salmon. Amphibia - Toad, frog, salamander, newts. Reptilia - Lizards, snakes. Aves (Birds) - Pigeons, ducks, domestic fowls, woodpeckers. Mammalia - Man, rabbit, rat.

WAEC Biology 2020 Theory — Question 4

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