1. DO NOW…
The diagram below provides information about a carrot cell.
A carrot cell contains 18 chromosomes. Which of the diagrams at the right illustrates the correct number of chromosomes in new cells produced by mitosis?

2. Meiosis Objectives: To describe the process of meiosis
To compare meiosis to mitosis

3. Comparing Cells Most cells in your body are diploid
2 sets of homologous chromosomes (2N)
i.e., 23 chromosomes from mom, 23 from dad
Gametes, or sex cells, are haploid
1 set of chromosomes (N)
23 chromosomes total
When sperm fertilizes egg  zygote

4. What happens during meiosis?
Diploid cells form haploid cells
The process occurs in 2 divisions:
Meiosis I
Meiosis II
Let’s take a look how…

5. View meiosis

6. Summing Up Before meiosis I begins, chromosomes replicate In meiosis I
Homologous pairs form tetrad (prophase I)
Crossing over may occur – increases variety
Homologous pairs line up in center of cell (metaphase I)
Homologous pairs are separated, but sister chromatids remain attached (anaphase I)
Results in 2 haploid cells

7. Before meiosis II, chromosomes do not replicate
Meiosis II resembles mitosis
Chromosomes with sister chromatids line up in center of cell (metaphase II)
Sister chromatids separate (anaphase II)
Final result is 4 haploid daughter cells

8. How does meiosis compare to mitosis?

9. Mitosis Meiosis Replicate once, divide once
2 daughter cells are identical to parent cell
Meiosis
Replicate once, divide twice
4 haploid daughter cells, not identical to parent or each other