Meiosis Why We Are Who We Are

Warm Up Why do you think you don’t you look exactly like your biological parents? Meiosis video

Meiosis Takes place in the Gametes (sex cells) of an organism People have a Chromosome count of 46 When an egg joins a sperm the count must stay at 46 to remain human So, the egg can only have 23 chromosomes, and the sperm can only have 23 chromosomes How does this happen?

+ = Sperm (23) + Egg (23) = Fertilized Cell (46) During Meiosis gamete (sex) cells undergo a “double division” reducing the chromosomal count to 23. + = Sperm (23) + Egg (23) = Fertilized Cell (46)

Original Gamete Metaphase Anaphase Telophase Cytokinesis 2 Daughter Cells Metaphase 2 Anaphase 2 Telophase 2 Cytokinesis – 4 Gametes

List the steps of the cell cycle in the mitosis column Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Mitosis Meiosis Purpose To make BODY cells To grow To repair injuries To make SEX cells for reproduction Sex cells = gametes = eggs and sperm cells

Mitosis Meiosis Which cells do it Happens in all BODY cells Happens in SEX organs of eukaryotes to make SEX cells

Mitosis Meiosis # Daughter Cells TWO daughter cells FOUR daughter cells

Mitosis Meiosis How much DNA In Eukaryotes, SAME amount of DNA as parent cell. Daughter cells identical to parent cell In Eukaryotes, HALF as much DNA as parent cell. Daughter cells are ready to combine with another sex cell to reproduce.

Mitosis Meiosis In Humans: TWO sets of 23 chromosome: One set inherited from mom and one set inherited from dad ONE set of 23 chromosomes: MIXED from parent’s DNA

Mitosis Meiosis Remember My-TOE- sis Mitosis makes body cells for growth and repair Mini-Meiosis Meiosis makes SEX cells to make a mini me.

Interphase Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokinesis

Meiosis ensures that all living organisms will maintain both Genetic Diversity and Genetic Integrity

4 2 2 46 23 SUPER SLUETH! How many divisions occur in Meiosis? How many cells result from the end of Meiosis one? How many cells are produced at the end of Meiosis two? How do sex cells differ from the parent cell? Meiosis begins with ______ chromosomes. Meiosis ends with ____ chromosomes. 4 2 2 46 23 ½ the chromosomes

These two girls are twins These two girls are twins. How is it possible that they look so differently?

4. Ending # of Chromosomes Mitosis Meiosis 1. What type of cells? 2. Starting # of Cells 3. Ending # of Cells 4. Ending # of Chromosomes

Meiosis Mitosis