The process of creating gametes Meiosis The process of creating gametes

Review of mitosis What is mitosis What are the stages of mitosis? What is the outcome of mitosis? Diploid- Haploid-

Meiosis Cellular process that reduces the number of chromosomes to produce gametes. What are gametes??? Sperm and Eggs Human body (somatic) cells have 46 chromosomes. How many chromosomes do sperm cells have? How many chromosomes do egg cells have?

Similarities Mitosis and meiosis are very similar, they begin the same way, but end very differently!

Interphase

DNA Doubles

DNA coils into Chromosomes

DNA condenses into Chromosomes

Prophase I Homologous pairs find each other

Crossing Over Crossing over is a complicated process that allows an exchange of genes, so that the offspring has more variety. This will not be demonstrated here.

Metaphase I

Anaphase I Spindle fibers attach to chromosomes and pull them apart

Chromosomes moving apart

Telophase I

Cell begins to split

2 new cells, exactly the same

Prophase II Chromosomes condense one more

Metaphase II Chromosomes line up in the middle again

Anaphase II Chromosomes begin pulling apart

Pulling apart

Telophase II

4 Haploid Cells

What is the purpose of reducing chromosomes??? 46 Sperm Egg +

A zygote (fertilized egg) with…. 92

With meiosis, there is a reduction in the number of chromosomes 23 Sperm Egg +

46

Animation http://www.teachertube.com/view_video.php?viewkey=dad03c61ca216b535145 http://www.johnkyrk.com/meiosis.html http://www.cellsalive.com/meiosis.htm http://www.pbs.org/wgbh/nova/baby/divi_flash.html http://www.sumanasinc.com/webcontent/animations/content/meiosis.html