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?

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

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

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…

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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

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

How does meiosis compare to mitosis?

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