Cell Growth and Reproduction

1. The Cell Cycle The cell cycle involves the growth, replication, and division of a eukaryotic cell. The two main phases of the cell cycle are interphase and M phase. During interphase, a cell's chromosomes are duplicated, but no cell division is occurring. Most of a cell's life is spent in interphase.

1. The Cell Cycle D. M phase includes mitosis and cytokinesis. E. During mitosis, the nucleus of a cell divides into two daughter nuclei that each contain the same number of chromosomes as the parent nucleus. F. The two nuclei that are formed during mitosis are separated into two identical daughter cells during cytokinesis.

1. The Cell Cycle

2. Cell Growth and Reproduction All cells come from pre-existing cells. Cell division is a key process involved in growth, repair, and reproduction of organisms. Cell division is triggered as cells become too large to efficiently import nutrients and export wastes across their cell membrane.

2. Cell Growth and Reproduction C. Cells will continue to divide until they fill up the space that they are in, once they begin to touch they stop. (Inhibition) D. Cellular reproduction occurs mainly by mitosis to create somatic (body) cells E. Mitosis only occurs in eukaryotes. F. Mitosis gives cloned or copied cells (skin cells make more skin cells etc…)

2. Cell Growth and Reproduction F. Basic chromosome facts Chromosomes are “books” of genetic information They resemble the letter “X”(double stranded chromosome) Each side of the “X” is called a chromatid (or single stranded chromosome)and they are copies of each other The chromatids are held together by a centromere

3. The Steps of the Cell Cycle A. Interphase- Interphase occurs before mitosis. During interphase, the chromosomes containing the genetic information of the cell are copied. G1, S, G2

3. The Steps of the Cell Cycle B. Prophase - Genetic material (chromatin) condenses into rod-like structures called chromosomes.

3. The Steps of the Cell Cycle C. Metaphase - Chromosomes line-up along the equator of the cell.

3. The Steps of the Cell Cycle D. Anaphase - Chromatids separate and move to opposite sides of the cell.

3. The Steps of the Cell Cycle E. Telophase and Cytokinesis - A nuclear membrane forms around each set of chromosomes, the cytoplasm divides (cytokinesis).

4. Meiosis a type of eukaryotic cell division that reduces the number of chromosomes in a cell by half. produces haploid (N) daughter cells that contain only half of the species' usual number of chromosomes. These resulting daughter cells are called gametes and aid the organism in sexual reproduction.

5. Steps of Meiosis A. Meiosis forms the sex cells of an organism, it cuts the complete chromosome number (diploid) in half (haploid) so that when two sex cells combine the diploid number is restored.

5. Steps of Meiosis B. Prophase I - homologous chromosomes pair and become tetrads (two chromosomes or four chromatids). Crossing over between homologous chromosomes occurs at this stage.

5. Steps of Meiosis C. Metaphase I - After crossing over occurs, homologous chromosomes line-up along the equator.

5. Steps of Meiosis D. Anaphase I - Whole (double stranded)chromosomes separate from the tetrad formation and move to opposite sides of the cell. Each chromosome still has two sister chromatids.

5. Steps of Meiosis E. Telophase I - a nuclear membrane forms around each set of chromosomes. Each cell now has one set of chromosomes and is haploid (n). Cytokinesis then also occurs.

5. Steps of Meiosis F. Prophase II - Sister chromatids become short and thickened.

5. Steps of Meiosis G. Metaphase II - The chromosomes migrate to the center of the nucleus and line-up along the equator by the end of metaphase II.

5. Steps of Meiosis H. Anaphase II - sister chromatids (double stranded chromosomes)are pulled apart.

5. Steps of Meiosis I. Telophase II - A nuclear envelope forms around each set of chromosomes and meiosis II is complete.

5. Steps of Meiosis Cytokinesis occurs and you have four haploid daughter cells. (gametes, sex cells)

6. Crossing Over A. Crossing over occurs during prophase I when two chromosomes pair up and exchange parts of their DNA. Crossing over provides genetic diversity between the parents and their offspring.