Question

1. Illustrate meiosis in the life cycle of a higher animal.

2. How does the amount of DNA per cell change during gametogenesis and fertilization?

3. Describe the movement of chromosomes during each stage of meiosis. At each stage, determine the number of bivalents, the number of chromosomes, the number of chromatids, and the relative amount of DNA.

4. Explain how recombination occurs between homologous chromosomes.

(Please answer all the questions)

Answer 1

Answer 1: Meiosis contribute to genetic variation.Meiosis do not make the body cells but it is responsible formation of sperm and ova that is haploid cell. The human life is the alternation of halving and doubling of chromosome number that takes place each generation. As human beings are multicellular organism which have 23 pair of chromosome.

.The life cycle of human follows the different steps during meiotic division:

Alteration : It is the stage where alternation of halving/ doubling of chromosome number takes place each generation which is completed into three steps

Step 1: Meiosis: here formation of haploid (n number) gametes takes place by the reduction of chromosome number. As we know that all the somatic cells are diploid in nature except gametic cell or sex cell which produce haploid gametes.

Step 2: Fertilization: In this stage the restoring of chromosome number takes place. Here in fertilization process sperm(n number) and ova(n number) combine each other during fertilization to form zygote(2n / diploid cell).

Step 3: Mitosis : Growth and development of organism takes place to develop in adult.