The diagram given below represents a certain phenomenon which occurs during meiosis. Name and explain the phenomenon by using the terms - homologous chromosomes, chromatids, and crossing-over.

Given below is a schematic diagram of a portion of DNA.

(a) How many strands are shown in the diagram?

(b) How many nucleotides have been shown in each strand?

(c) Name the parts numbered 1,2,3,4 and 5 respectively.

(d) Name the DNA unit constituted by the parts 1, 2 and 3 collectively.

The diagram below represents a stage during cell division. Study the same and then answer the questions that follow:

a. Name the parts labelled 1, 2 and 3.

b. Identify the above stage and give a reason to support your answer.

c. Mention the type of cells in our body where this type of cell division occurs.

d. Name the stage prior to this stage and draw a diagram to represent the same.

Draw a labelled diagram to show the metaphase stage of mitosis in an animal cell having "6" chromosomes.