STD X – BASIC BIOLOGY – NEWTON

Types of Cell division

Cell division:

It is a process by which one single cell gives rise to two or more cells.

Cell division is of two types, namely:

Mitosis

meiosis

Mitosis:

In this, cell division leading to growth and development and seen in vegetative cells of the body.

During mitosis, the parent cell divides into two daughter cells, which are not only identical to each other but also to the parent cell. Mitosis is also known as equational division, as both the parent and the progeny cells have the same number of chromosomes.

Mitosis is divided into four stages of nuclear division, namely

Prophase.

Metaphase.

Anaphase.

Telophase.

The structure of Chromosomes

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

Chromosomes are made of 50% proteins, and 50% DNA (deoxyribonucleic acid). Chromosomes are made of many chromatin threads, each containing DNA and proteins.

Somatic cells contain 46 chromosomes, gametic cells contain 23 chromosomes.44 of our chromosomes are AUTOSOMES, while 2 are called sex chromosomes. Each chromosome contains many GENES that act as a blueprint or set of instructions for the cell.