Mitosis and Meiosis
By Tatiana and Clara 2G
Mitosis
Mitosis is the name for making new cells. The new cells are genetically identical to the original cell. The original cell(s) are called parent cells and the new cell(s) are called daughter cells. You need to make new cells for growth and repair e.g organs and tissues.
DNA Replication
In order for a cell to divide the original DNA, inside the cell, must first make a copy of itself. This is called DNA replication:
Stage 1 DNA Replication
The parent DNA starts unzipping, the bases are split apart.
Stage 2 DNA Replication
The unzipped halves of DNA strands act as a template to form a new DNA strand.
Stage 3 DNA Replication
Two copies made containing half the original DNA and half of the newly made DNA.
Meiosis
Meiosis is the cell division of sex cells-the gametes.
The gametes are different to the normal cells because they contain HALF the number of chromosomes.
Normal cells- 46
Gametes- 23
They have this, because when the two types of Gamete (sperm cells and egg cell) join together, they have 46 chromosomes.
First/second stage of Meiosis
The parent cell starts off with a complete set of chromosomes. DNA replication occurs, the chromosomes line up and the "cross over" of genes occurs.
Third stage of meiosis
Two daughter cells are produced with a complete set of chromosomes.
Fourth stage of meiosis
Four non-identical cells are then produced with half the number of chromosomes.