Science revision

Meiosis, gametes and fertilisation

Biology

Meiosis:

• Meiosis is another type of cell division, it creates gametes (sex cells)
• Meiosis forms gametes in the womens ovaries and mens testes. 
• Mammals body cells are diploid. This means that each body cell contains two copies of each chromosome in its nucleus. One from the organisms mum and one from the dad.

Meiosis involves two divisions:

• Similar to mitosis, meiosis starts in the same way. The DNA replicates and forms a double-armed chromosomes.
• After the replication the chromosomes get into pairs. Humans have 23 pairs of chromosomes, thats 46 altogether. In meiosis each pair of chromosomes contain exactly the same features, just like mitosis however one chromosome comes from your mum and one from your dad.
• When the cells divide at first the pairs then split up, the chromosome from each pair moves to…