Question

In a homozygous plant round seeds (R) are dominant over wrinkled seeds (r).
$\left(i\right)$Draw a Punnett square to show the gametes and offspring when both the plants have heterozygous round seeds (Rr).
$\left(ii\right)$ Mention the phenotype and genotype ratios of the offsprings in $F_2$ generation.
$\left(iii\right)$ Name the sex chromosomes in human males and females.
$\left(iv\right)$ Briefly explain the term mutation.
$\left(v\right)$ What is the number of chromosomes in the gametes of human beings?

Answer 1

(ii) Genotype ratio is 1:2:1, RR : Rr : rr

Phenotype ratio is 3:1, round seeds : wrinkled seeds

(iii) There are two sex chromosomes in human, X and Y. Females have XX chromosomes and males have XY chromosomes.

(iv) Mutation refers to the changes in the nucleotide sequence of DNA which can be inherited.

(v) The number of chromosomes in human beings are 23 pairs, that is 22 pairs of autosomes and one pair of sex chromosome. Thus, the gamete will have 23 chromosomes.