Meiosis Chromosomes In the nucleus of each cell

Meiosis

Chromosomes In the nucleus of each cell during replication, the DNA molecule is packaged into thread-like structures called chromosomes.

Chromosomes Somatic (body) cells in sexually reproducing organisms are diploid Diploid (2 N) cells containing “two sets” of homologous chromosomes, one copy from the male parent and the other from the female parent

Chromosomes Reproductive cells are haploid. Haploid (N) a cell that contains “one set” of chromosomes

Meiosis A form of cellular division that halves the number of chromosomes when forming specialized reproductive cells called gametes.

Meiosis In meiosis there are two rounds of divisions in which the nucleus divides twice. Meiosis I & Meiosis II

Meiosis Interphase The cell grows and duplicates its DNA and centrioles

Meiosis I Prophase I The chromosomes condense, nuclear envelope breaks down, homologous chromosomes form tetrads, and crossing-over occurs.

Meiosis I 2 N=4

Crossing Over

Meiosis I Metaphase I The pairs of homologous chromosomes line up in middle.

Meiosis I Anaphase I The pairs of homologous chromosomes separate and are pulled/pushed to the poles.

Meiosis I Telophase I The pairs of homologous chromosomes gather at poles, nuclear envelope reforms, chromosomes relax into chromatin. Cytokinesis: The cytoplasm divides.

Meiosis I

Meiosis II Prophase II The chromosomes condense, nuclear envelope breaks down, and new spindle fibers form around chromosomes.

Meiosis II Metaphase II The chromosomes line up in middle of cell.

Meiosis II Anaphase II The chromosomes separate and are pulled/pushed to poles.

Meiosis II Telophase II The chromosomes gather at poles, nuclear envelope reforms, chromosomes relax into chromatin. Cytokinesis: The cytoplasm divides to form gametes.

Meiosis II

Meiosis in a minute…

Meiosis in Males Spermatogenesis The process by which sperm is produced in male animals. Spermatogenesis occurs in testes. 1. During Meiosis I the diploid cell increases in size becoming a germ cell to undergo Meiosis. 2. The larger germ cell undergoes Meiosis II to form 4 haploid cells, which develop tails and become sperm.

Meiosis in Females Oogenesis The process by which an ovum is produced in female animals. Oogenesis occurs in ovaries. 1. During Meiosis I & II the cytoplasm divides unequally. 2. The larger germ cell undergoes Meiosis to an egg cell the other cell called a polar body eventually dies.

Males vs. Females

Meiosis Poster Presentation Instructions: Students will be working in predetermined pairs to create posters. Students will be creating a poster depicting one of the eight stages of Meiosis. Once posters are complete students will work as a group to place them in the correct order. One pair will be selected to explain the entire process to the class using the posters.

Meiosis Flipbook Instructions: • Students may work in their pairs but each student is to create their own flipbook. • Each student is to collect 9 index cards and 1 clip. Materials will be located in the front of the room. • Using the blank side of the index cards draw each of the phases of Meiosis including Interphase. • On the lined side of the index card briefly describe what is happening during that particular phase.