a. Explain briefly the following terms: i. gene;... | WAEC SSCE - Biology - 2018 (Essay)

Question 1 Report

a. Explain briefly the following terms:
i. gene;
ii. Hybrid;
iii. Trait.

(b) Two heterozygous yellow flowers are crossed. Using a genetic diagram, state the phenotypic and genotypic ratios of the first filial generation.

Answer

Answer Details

(a) Explanation of terms

(i) Gene: a unit of hereditary material, a length of DNA on a chromosome, that carries the code for a particular characteristic and is passed from parent to offspring.
(ii) Hybrid: the offspring produced from a cross between two genetically different (unlike) parents; in genetics a heterozygote carrying two different alleles of a gene.
(iii) Trait: an observable inherited characteristic or feature of an organism, such as flower colour or height.

(b) Cross between two heterozygous yellow flowers

Let \(Y\) = allele for yellow (dominant) and \(y\) = allele for the recessive colour. Each heterozygous parent is \(Yy\).

Parental genotypes: \(Yy \times Yy\)

Gametes: \(Y\) and \(y\) from each parent.

Gametes	Y	y
Y	YY	Yy
y	Yy	yy

Genotypic ratio of F1: \(1\,YY : 2\,Yy : 1\,yy\).

Phenotypic ratio of F1: 3 yellow : 1 recessive (non-yellow), i.e. \(3:1\).

(c) Four transmitted (inherited) characters in plants

a. Explain briefly the following terms: i. gene; ii. Hybrid; iii. Trait. (b) Two heterozygous yellow flowers are crossed. Using a genetic diagram, state the...