Answer the following question in a complete sentence. 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? How do you know?

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

Mitosis Review The process of cell division Occurs in somatic cells which are all the cells in your body except egg and sperm cells 2N Diploid  meaning that it has two of each chromosome These two chromosomes are identical in mitosis

I. Meiosis Process of making sex cells called gametes Male gametes are sperm Female gametes are eggs Sex cells have half the number of chromosomes as other cells N (haploid) When sperm fertilizes egg  zygote 2N (diploid) – it has 2 of each chromosome, 1 from mom, 1 from dad

II. Meiosis occurs in 2 divisions Interphase I - Before meiosis, cells in testes/ovaries copy DNA Meiosis I Prophase I - Chromosomes with same type of genetic information (homologous chromosomes) match up these chromosomes may “swap” genes in a process called crossing over Metaphase I - Homologous pairs line up in middle of cell RANDOMLY Anaphase I - Pairs split up Telophase I – Cell membrane begins to pinch in and results in 2 daughter cells are different from each other & parent cell

Between meiosis I and meiosis II, DNA does not copy again Meiosis II is like mitosis Prophase II Metaphase II - Chromosomes line up in center of cell Anaphase II - Chromosomes split apart & move into daughter cells Telophase II - Nucleus forms around each set of chromosomes End result: 4 daughter cells that are each unique

View meiosis

III. How does meiosis compare to mitosis?

Mitosis 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