Cell division – ‘reduction division’
Production of sex cells – gametes
Meiosis is necessary to halve the number of chromosomes going into the sex cells
Why halve the chromosomes in gametes?
At fertilisation the male and female sex cells will provide ½ of the chromosomes each – so the offspring has genes from both parents
Parent cell – chromosome pair
1st division - pairs split
2nd division – produces 4 gamete cells with ½ the original no. of chromosomes
Meiosis – division error
Should the gamete with the chromosome pair be fertilised then the offspring will not be ‘normal’.
In humans this often occurs with the 21st pair – producing a child with Downs Syndrome
Can you see the extra 21st chromosome?
Is this person male or female?