Pass up your signed progress reports & then open your notebooks to the journal section

Journal #6 10/1, 10/2 What part of the cell cycle does the cell stay in the longest? Why?

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Section 10-2 Figure 10–5 Mitosis and Cytokinesis Go to Section:

Meiosis *Gametes are special cells used in sexual reproduction. It is important that these cells contain 1/2 the normal number of chromosomes than the regular body cells. *When the sperm and egg unite the resulting zygote will contain the normal number of chromosomes for that organism

Mitosis- formation of body cells. At the end of mitosis each of the 2 daughter cells has 46 chromosomes These are your body cells, cells that make up tissues, organs, etc Meiosis-formation of sex cells called gametes. At the end of meiosis each of the 4 daughter cells has 23 chromosomes. They contain half the number of chromosomes

Cell division cell type # of daughter # of cells chromosomes Mitosis somatic(body) 2 46(diploid) Meiosis gametes(sex) 4 23(haploid) Meiosis reduces the number of chromosomes to half the number in body cells. This is called the haploid number. Reductive division is necessary so that when reproduction occurs, the zygote contains the necessary 46. Egg(23 chrom) + sperm(23 chrom) = zygote(46 chrom)

Meiosis There are 2 divisions of meiosis- Meiosis I and Meiosis II. It must be this way in order to end up with the sex cells only having 23 chromosomes.

Meiosis I During the first meiotic division, chromosomes are replicated. 1. Prophase I- chromatin makes a copy of itself and begins to coil up

2. Metaphase I- homologous pairs of chromosomes line up together at the middle of the cell. This forms a tetrad(meaning 4). Homologous chromosomes are paired chromosomes. Each contains genes for the same trait.

3. Anaphase I- homologous chromosomes that form each tetrad separate and move to opposite ends. The centromeres do not split.

4. Telophase I- spindle disappears and the cell divides.

Meiosis II During the second meiotic division, nothing is replicated. 1. Prophase II- centriole doubles, spindle forms

2. Metaphase II- chromosomes line up at the middle

3. Anaphase II- individual chromatids move to opposite ends

4. Telophase II- when the 2 daughter cells divide into 4 new daughter cells, each new daughter cell has 23 chromosomes. This is half the number of the original parent cell.

Meiosis Meiosis occurs in the testes of the male and is called spermatogenesis. 4 sperm are produced. And in the ovaries of the female it is called oogenesis. 4 cells are produced but only 1 becomes an egg, the other 3 dissolve.

Quiz #2 -yes we never had time to take quiz one, skip it, no that doesn’t mean you get a hundred for it Michael. Meiosis

1.Meiosis is the process of forming _____ cells. a. gameticb. somatic c. body 2.Gametes contain ________ chromosomes. a. 25 b. 46c. 23d There are ___ divisions of meiosis. a. 3b. 4 c. 2 d. 5 4.Meiosis in males leads to the production of 4 __ cells. a. eggb. spermc. ovum 5.At the end of ___ in meiosis I, 2 daughter cells are formed. a. interphase b. metaphase c. telophase d. anaphase