1. Why do we care about Meiosis?  It determines what sex cells will be created!  A baby’s characteristics and traits will be determined based on the characteristics of the sperm and egg cells combined.  Are you telling me that if a different sperm and egg cell had combined I might look extremely different?  I SURE AM!! That’s why we care about Meiosis!

2. We need a bit of background information before we can start.  Chromosomes are composed of sections of DNA  Individual sections of DNA that determine a specific characteristic are called a gene For example: Gene for eye color, hair color etc.

3. Genes on a chromosome  Stripes on the chromosomes represent sections of DNA which are genes  Every cell has 2 of every chromosome. These have the same type of genes.  EX: You have 2 chromosomes that have genes for eye color, hair color ear shape. One May be for brown eyes, the other for blue  1 is given from mom, 1 is given from dad when sperm and egg cells combine.  These are called Homologous chromosomes.

4. Every organism has a unique number of chromosomes  Fruit flies have 8 chromosomes (4 from their mom, 4 from their dad)  Chimpanzees have 48 chromosomes 24 from mom and 24 from dad  Humans have 46 chromosomes. 23 are from mom 23 are from dad.

5. Get ready to crunch some numbers! To create sperm and egg cells DNA is replicated in each cell. The orgininal cell has _______chromosomes. The new cell has ________ 46,92 The cell divides. 2 cells now have _____chromosomes 46 The cell divides again…4 cells now have ______ chromosomes 23! Why is it crucial to only have 23 chromosomes? _________________________________

6. Thus MEIOSIS!!!!!  Lets go through it step by step!! Take out your worksheets! Note…  In Mitosis we start with the same amount of chromosomes that we end with.  In Meiosis we end with ½ the amount of chromosomes we start with.  chromosomes will overlap along the way which will cause different combinations of the father and mothers genes to be created on chromosomes…  This is why siblings can look so different  This creates genetic diversity…….

7. Things to remember  The chromosomes overlap  This creates 4 Unique chromosomes that will end up in 4 different sperm or egg cells.  Homologous chromosomes line up on one side sometimes and the other side other times which increases the chances of diverse sperm and egg cells.