Why Do cells Go through Meiosis? Cells go through Meiosis in order to make Sex Cells Sex cells are also called Gametes Four Daughter Cells are created Haploid (1N)

Interphase Cell Grows Duplicates DNA Cell Prepares to divide

After Interphase In order to make sex cells or cells with half the number of chromosomes meiosis has TWO phases Meiosis I and Meiosis II

Prophase I Chromosomes Condense (visible) Homologous chromosomes form a tetrad Crossing Over Occurs

Crossing Over Homologous Chromosomes- Similar Chromosomes, Same genes in the same location When the chromosomes touch they switch genes Causes genetic variation

Metaphase I Homologous chromosomes move together to the middle of the cell Spindle attaches to the centromere

Anaphase I Homologous chromosomes separate Sister chromatids stay attached Move towards opposite poles

Telophase I Division of cytoplasm Creates Two daughter cells Begin Meiosis II There is no interphase II Why?

Prophase II Spindles re-appear Nuclear membrane stays separated

Metaphase II Chromosomes line up in the middle Spindle attaches How are metaphase I and II different?

Anaphase II Sister Chromatids Separate from each other How are Anaphase I and II different from each other?

Telophase II Nucleus reforms Division into four daughter cells Haploid (1N) Gametes (egg and sperm)

Mitosis & the Cell Cycle

Cell Growth & Development Are cells of organisms the same size? Do your cells get bigger as you grow, or do you just produce more cells? Are cells of organisms the same size? Do your cells get bigger as you grow, or do you just produce more cells? When talking about Cell Size…… Smaller is Better! When talking about Cell Size…… Smaller is Better! The larger a cell becomes, the more demands the cell places on its DNA, and the harder it is to supply with nutrients. The larger a cell becomes, the more demands the cell places on its DNA, and the harder it is to supply with nutrients.

Cell Division Before a cell becomes to large, a growing cell will divide. Before a cell becomes to large, a growing cell will divide. Cell division is the process by which a Single cell divides into 2 Daughter cells. Cell division is the process by which a Single cell divides into 2 Daughter cells. Cell Division = the series of events that cells go through as they grow and divide. Cell Division = the series of events that cells go through as they grow and divide.

Chromosomes Chromosomes= are composed of DNA- Which carries the cell’s coded genetic information. Chromosomes= are composed of DNA- Which carries the cell’s coded genetic information. Humans have 46 chromosomes(23 pairs). Humans have 46 chromosomes(23 pairs). The chromosomes consist of two identical sister chromatids. The chromosomes consist of two identical sister chromatids.

Two Major Types of Cell Division Mitosis- Somatic cells (Body Cells) Mitosis- Somatic cells (Body Cells) Diploid 2N Diploid 2N Meiosis- Sex cells/ Gametes Meiosis- Sex cells/ Gametes Haploid 1N Haploid 1N

Mitosis Mitosis is the process by which the genetic information is replicated and distributed to daughter cells. Mitosis is the process by which the genetic information is replicated and distributed to daughter cells. 2 diploid(2N) daughter cells are produced from 1 diploid (2N) parent cell. 2 diploid(2N) daughter cells are produced from 1 diploid (2N) parent cell. The Daughter cells are genetically identical to the parent cells. The Daughter cells are genetically identical to the parent cells. There are 4 major stages to mitosis, Not including interphase. There are 4 major stages to mitosis, Not including interphase.

Interphase Interphase= The cell spends most of its life here; not part of the actual reproduction. NOT PART OF MITOSIS. Interphase= The cell spends most of its life here; not part of the actual reproduction. NOT PART OF MITOSIS. Cell grows and replicates its DNA and centriole Cell grows and replicates its DNA and centriole Nuclear membrane is visible Nuclear membrane is visible Nucleus, Nucleoli, and chromatin can be seen. Nucleus, Nucleoli, and chromatin can be seen.

Interphase

Prophase Prophase: first phase of Mitosis Prophase: first phase of Mitosis Nuclear membrane breaks down Nuclear membrane breaks down Chromosomes become visible Chromosomes become visible Centrioles separate Centrioles separate Spindle forms Spindle forms

Metaphase Metaphase: Second part of Mitosis Metaphase: Second part of Mitosis Chromosomes attach to spindle Chromosomes attach to spindle Chromosomes line up across the MIDDLE of the cell Chromosomes line up across the MIDDLE of the cell

Anaphase Anaphase: Third step in Mitosis Anaphase: Third step in Mitosis The sister chromatids separate and move apart towards opposite poles The sister chromatids separate and move apart towards opposite poles

Telophase Telophase: Fourth stage of Mitosis Telophase: Fourth stage of Mitosis Chromosomes gather at opposite ends of the cell Chromosomes gather at opposite ends of the cell The nuclear membrane begins to form and enclose the chromosomes The nuclear membrane begins to form and enclose the chromosomes Cell membrane begins to move inwards Cell membrane begins to move inwards

Cytokinesis Cytokinesis : Final stage in cellular division Cytokinesis : Final stage in cellular division Not Mitosis Not Mitosis Works with telophase Works with telophase The cytoplasm divides completely in half. The cytoplasm divides completely in half. 2 daughter cells with identical genetic information are produced. 2 daughter cells with identical genetic information are produced.