BIOLOGY UNIT 3- CELL DIVISION

What are chromosomes made up of?

Chromosomes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis.

What is a gene?

A section of DNA which codes for a protein.

How many chromosomes are found in the nucleus of human body cells?

46

How many chromosomes are found in the nucleus of the gametes?

23

How are chromosomes arranged in the nucleus of the body cell?

46 chromosomes are arranged in 23 pairs.

What are the 3 main stages of the cell cycle?

1. Replication of DNA and synthesis of organelles

2. Mitosis

3. Division of cell

Why is mitosis important?

1. Produces identical cells which all have the same genetic information

2. Produces additional cells for growth and repair

Describe the first stage of the cell cycle

Longest stage- cells grow and increase in mass, replicate DNA and synthesise more organelles .e.g. mitochondria, ribosomes

Describe the second stage of the cell cycle.

Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.