16
Which part of the human body should one use to demonstrate stages in mitosis?
Explanation
All the cells in the human body are somatic cells except germinal cells in the male and female reproductive organs. The somatic cells divide by mitotic cell division for growth and regeneration. These can be used to demonstrate mitosis.
17
What attributes does a chromatid require to be classified as a chromosome?
Explanation
Chromatid is one copy of a duplicated chromosome, which is joined to the other copy centromere. The duplication of chromosome material takes place at synthetic phase of cell cycle.
During mitosis, late metaphase and early anaphase, there is longitudinal splitting of chromosomes and thus two chromosome get separated, to get divided into the daughter cells.
18
The diagram shows a bivalent at prophase-I of meiosis. Which of the four chromatids can cross over?
Explanation
The homologous chromosomes lie parallel to each other in leptotene stage. Each chromosome has four chromatids and are bivalent. The non-sister chromatids of homologous chromosomes cross over in pachytene stage of prophase- I.
19
If a tissue has at a given time 1024 cells, how many cycles of mitosis had the original parental single cell undergone?
Explanation
The parental cell undergoes 10 divisions of mitotic cycle to give 1024 cells.
20
An anther has 1200 pollen grains. How many pollen mother cells must have been there to produce them?
Explanation
Three hundred pollen mother cells have to be there to produce 1200 pollen grains. because one pollen mother cell will produce four pollen grains.