1. Biology Meiosis Notes 01/04/2012

2. Goals for the day 1.Be able to describe the differences between mitosis & meiosis 2.Be able to describe what a homologous chromosome is 3.Be able to describe crossing over & why it is important

3. Question of the Day Where do you get your chromosomes (DNA) from?

4. Prokaryotes vs. Eukaryotes Prokaryotes – Asexual Reproduction – MOST Eukaryotes – Sexual Reproduction-

6. Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half?

8. Human Egg and Sperm cells have 23 chromosomes in them. How many chromosomes are in human egg and sperm cells?

9. Haploid – a half set of chromosomes (only found in sex cells) Diploid – a full set of chromosomes (found in all body cells, except sex cells- Body Cells AKA somatic cells)

10. How many chromosomes do humans have in their cells? How many chromosomes would be in a human diploid cell? How many chromosomes would be in a human haploid cell?

11. Homologous Chromosomes – chromosomes that have the same (homo) information Homologous Chromosomes pair up during Prophase 1 of meiosis Homologous Chromosomes Pairing

12. Homologous chromosomes sometimes switch parts this is called crossing over Crossing Over - acts as a source of variation within a species - Crossed over

13. In Metaphase 1 of meiosis homologous chromosomes are pulled apart (instead of sister chromatids, as in mitosis) This reduces the chromosome number by ½ in the first division, which is why meiosis 1 is known as the reductive division.

14. Diploid Number = Haploid number =

18. Meiosis in males makes 4 equal sperm Meiosis in females makes 1 huge egg

19. Cats have 38 chromosomes in their diploid cells. How many do they have in their haploid cells?

20. Chickens have 78 chromosomes in their body cells how many chromosomes do they have in their sex cells?

23. Karyotype – a picture of chromosomes Males – XY Females XX

24. Assignment A. Use your book (start on pg 192) to Define the following: 1.Haploid 2. Diploid 3. Gamete 4. Zygote 5. Sex Cell 6. Egg 7.Sperm B.Describe the difference between Meiosis 1 & Mitosis (think about homologous chromosomes) C.Define crossing over, genetic recombination and describe the effects this has on the genetic relationship of parent & offspring