Meiosis Cell division for the production of sex cells
Why do we need meiosis? <ul><li>Meiosis is necessary to cut the number of chromosomes going into the sex cells by half. </...
Do the math! <ul><li>each somatic cell (normal cell in the body) has 46 chromosomes in 23 pairs </li></ul><ul><ul><li>this...
Meiosis – What happens when chromosomes don’t split correctly? gamete has extra chromosome  Normal! split looks like this ...
Meiosis error - fertilization If the gamete with the extra chromosome gets fertilized, then the offspring will not be ‘nor...
21 trisomy – Downs Syndrome Can you see the extra 21 st  chromosome? Is this person male or female?
Meiosis – without error Parent cell – chromosome pair Chromosomes copied 1 st  division - pairs split 2 nd  division – pro...
Meiosis  Parent cell 4 gametes 1 st   division 2 nd  division
Overview of Meiosis
Put the images in the correct order
This powerpoint was kindly donated to  www.worldofteaching.com http://www.worldofteaching.com  is home to over a thousand ...
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Meiosis

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Meiosis

  1. 1. Meiosis Cell division for the production of sex cells
  2. 2. Why do we need meiosis? <ul><li>Meiosis is necessary to cut the number of chromosomes going into the sex cells by half. </li></ul><ul><li>Why halve the chromosomes in gametes? </li></ul><ul><li>At fertilization, the male and female sex cells will provide ½ of the chromosomes each to the new zygote (future baby) </li></ul><ul><ul><li>so the offspring has genes from both parents </li></ul></ul>
  3. 3. Do the math! <ul><li>each somatic cell (normal cell in the body) has 46 chromosomes in 23 pairs </li></ul><ul><ul><li>this is the proper number for the cell to function correctly </li></ul></ul><ul><ul><li>more or fewer chromosomes lead to problems or cell death </li></ul></ul><ul><ul><li>mitosis keeps this number the same each time a cell divides </li></ul></ul><ul><li>Meiosis takes the number of chromosomes down to 23 (half the full set), so that when an egg is fertilized by a sperm the new zygote has 46 chromosomes </li></ul><ul><ul><li>Without this the zygote would get 92 chromosomes, which is WAY TOO MANY! </li></ul></ul>
  4. 4. Meiosis – What happens when chromosomes don’t split correctly? gamete has extra chromosome Normal! split looks like this side Error! too many chromosomes in these gametes
  5. 5. Meiosis error - fertilization If the gamete with the extra chromosome gets fertilized, then the offspring will not be ‘normal’. In humans this often occurs with the 21 st pair – producing a child with Down Syndrome
  6. 6. 21 trisomy – Downs Syndrome Can you see the extra 21 st chromosome? Is this person male or female?
  7. 7. Meiosis – without error Parent cell – chromosome pair Chromosomes copied 1 st division - pairs split 2 nd division – produces 4 gamete cells with ½ the original number of chromosomes
  8. 8. Meiosis Parent cell 4 gametes 1 st division 2 nd division
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  11. 11. Overview of Meiosis
  12. 12. Put the images in the correct order
  13. 13. 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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