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Meiosis

Meiosis. Cell division – ‘ reduction division’ Production of sex cells – gametes Meiosis errors. Why do we need meiosis?. Meiosis is necessary to halve the number of chromosomes going into the sex cells Why halve the chromosomes in gametes?

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Meiosis

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  1. Meiosis Cell division – ‘reduction division’ Production of sex cells – gametes Meiosis errors

  2. Why do we need meiosis? • 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

  3. Meiosis Parent cell – chromosome pair Chromosomes copied 1st division - pairs split 2nd division – produces 4 gamete cells with ½ the original no. of chromosomes

  4. Meiosis – mouse testes Parent cell 1st division 2nd division 4 gametes

  5. Meiosis – division error Chromosome pair

  6. Meiosis error - fertilisation 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

  7. 21 trisomy – Downs Syndrome Can you see the extra 21st chromosome? Is this person male or female?

  8. This powerpoint was kindly donated to www.worldofteaching.com http://www.worldofteaching.com is home to over a thousand powerpoints submitted by teachers. This is a completely free site and requires no registration. Please visit and I hope it will help in your teaching.

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