Question

3(a) Explain four causes of damage to maize during storage.
(b) Two heterozygous tall plants, Tt, were crossed in an experiment. Using a genetic diagram: (i) show the possible offspring that could result from the cross; (ii) determine the: I. genotypic ratio of the offspring; II. phenotypic ratio of the offspring.
(c) State Mendel's law(s) of inheritance.
(d) Mention two forage grasses.

Accepted Answer

(a) Causes of damage to maize during storage: insect pests; rodents; fungi (moulds); poor storage conditions (e.g. hot and humid conditions).

(b)(i) Genetic cross Tt × Tt:
Parents: Tt × Tt
Gametes: T, t × T, t
Offspring genotypes: TT, Tt, Tt, tt
(ii) I. Genotypic ratio = 1 TT : 2 Tt : 1 tt (1:2:1)
II. Phenotypic ratio = 3 tall : 1 short (3:1)

(c) Mendel's first law (Law of Segregation): the characteristics of an organism are controlled by genes which occur in pairs; only one of such a pair of genes can be carried in a single gamete.
Mendel's second law (Law of Independent Assortment): alleles of one trait assort independently from the alleles of another trait, and are distributed to daughter nuclei with equal probability.

(d) Forage grasses: Guinea grass; Elephant grass; Fescues; Bromegrasses.

WAEC Agricultural Science 2022 Theory — Question 3

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