Meiosis Powerpoint Notes

Disease #___ Meiosis Presentation Notes Integrated Science 2 Name: Per: Meiosis: The Formation of Sex Cells  You simply cannot combine an egg and sperm if they contain the number of !  The chromosome number must be reduced to . This is ! I. Overview of Meiosis A. All organisms inherit complete sets of genes, one from .  In animals, mom’s set of genes comes from an cell; dad’s set of genes comes from a cell  In plants, the genes come from and . B. Sex cells, or contain of the normal amount of chromosomes. 1. Meiosis is the process of creating (N) gametes from (2N) cells  Occurs in eukaryotic cells only  Required for sexual, but not asexual reproduction II. Chromosome Number A. Eukaryotic sexual reproduction results in organisms with two sets of chromosomes 1. The two sets are said to be a. chromosomes in one set have a of themselves in the other set. B. A cell with both sets of is said to be . 1. Ex. (liver cell, heart cell, skin cell etc.) C. A cell with one set of is said to be . 1. Ex. (egg and sperm or ovule and pollen)

Each body cell of a fruit fly has 8 chromosomes, 4 from the Each body cell of a human has 46 chromosomes, 23 from the male and 4 from the female male and 23 from the female

III. Phases of Meiosis Overview: Diploid cells destined to become gametes go through rounds of cell division. A. DNA Replication 1. occurs before the round of cell division. (Recall the S phase of mitosis) B. Meiosis I 1. newly synthesized chromosomes pair up with their , forming a . Draw a tetrad in the box to the right.

 Ex. The chromosomes containing the gene for eye color from mom will pair up with the chromosome containing the gene for eye color from dad.

 This is different from mitosis! 2. the tetrads may portions of their chromatids in a process called

 are exchanged between homologous chromosomes  this introduces ! 3. Homologous chromosomes and the cell 4. new (N) cells are formed, each having a unique set of genes. C. Meiosis II 1. Performed by the two new cells produced in  each of the new haploid cell’s chromosomes contains 2 unique chromatids 2. DNA does replicate! 3. Prophase through cytokinesis occurs. 4. unique (N) cells are formed  two from each of the cells produced in meiosis I. Males vs. Females  The formation of sperm cells is called  The formation of egg cells is called  For animals, meiosis in males produces sperm from every germ cell vs. egg for females. - In females, 3 polar bodies (except DNA) and . IV. Mitosis vs. Meiosis A. Mitosis  _ reproduction - Begins with a diploid cell (2N)  Results in the formation of cells (2N) that are genetically to each other and to the original cell B. Meiosis  _ reproduction - Begins with a diploid cell (2N)  Results in the formation of cells (N) that are genetically from each other and the original cell