CHROMOSOMES AND SEX DETERMINATION

1. Define chromosomes and describe its structure.
- The ribbon shaped clear, thick and long microscopic threads which can be seen during the cell division are called chromosomes. Its structure can be described in following points:
a. Chromosomes have many genes.
b. Each chromosome is made up of DNA and protein.
c. Each chromosome has constriction.

2. Define centromere or kinetochore.
- The constriction present in the chromosome is called  centromere or kinetochore.

3. Enlist the function of chromosomes.
- The function of chromosomes are as follows-
a. They determine the characteristics of plant and animals.
b. It transfer characteristics from one generation to another.

4. Describe types of chromosomes on the basis of position of centromere.
- On the basis of position of centromere, chromosomes are divided into four types:
a. Metacentric chromosomes-  It has centromere in middle of chromosome. Both arms of chromosomes are equal.
b. Sub-metacentric chromosomes- It has centromere near the middle of chromosome. Both arms are unequal.
c. Acrocentric chromosomes- It has centromere near the end of chromosome.
d. Telocentric chromosomes- It has centromere at the end of chromosomes.

5. What are the types of chromosome on the basis of characteristics?
- On the basis features, chromosomes are divided into two types:
a. Autosome:  Autosomes determine the characteristics of the body. There are 22 pairs of autosomes in the nucleus in the nucleus of the human body cell.
b. Sex chromosome: Sex chromosome determines the sex of upcoming generation. In the nucleus of human body cell, there are 1 pair of sex chromosomes (XX OR XY) .

6. What are the type of cell on the basis of number of chromosomes?
- On the basis of number of chromosomes cells are divided into two types:
a. Diploid cells- The cells in which half the number of chromosomes come from the mother and half from father to make "2n" are called diploid cells. Generally somatic cells are diploid.
b. Haploid cells- Cells with the half number of chromosomes are called haploid cell. They are denoted by "n".