G. Holmes Braddock High School Mitosis & Meiosis G. Holmes Braddock High School

Lesson Guide Mitosis Meiosis Cell Cycle Sexual & Asexual Reproduction Genetic Variation and Cancer

Mitosis Mitosis is the process in which the division of cells occurs. Mitosis happens in all cells except sex cells. Before mitosis the cells chromosomes double(turns into diploid cell). then half when the cell splits, leaving the original number of chromosomes in the two new daughter cells(forming two new haploid cells). Interphase : (Cell Cycle) The cell grows and doubles its chromosomes. Prophase : The chromatin inside the nucleus condenses into chromosomes while spindle fibers begin to form at opposite ends/”poles” of the cell. Metaphase : As the spindle fibers fully develop they stretch out towards the center of the cell. The chromosomes of the cell move towards the metaphase plate (center of the cell).

Mitosis Anaphase : The paired chromosomes divide into chromatids and begin to be pulled towards opposite ends of the cell by the spindle fibers. Telophase : New nuclei form at the two ends of the cell with their corresponding chromosomes. The cell begins to divide into its two new daughter cells. Cytokinesis : The cell is completely divided in two, forming two new daughter cells.

Meiosis Meiosis is the process of cell division in sex cells. Similar to mitosis, when a cell undergoes meiosis, it first doubles its chromosomes before it splits and divides into two new cells, ending meiosis 1. The new cells then begin meiosis 2. During meiosis 2 the cells do not multiply their chromosomes before splitting, both cells divide creating four new daughter cells each containing half the amount of chromosomes of an original cell. These new daughter cells are called gametes, also known as the sperm cells in males and the egg cells in females. Meiosis 1 Interphase : In this stage the cell grows and doubles its chromosomes.

Meiosis Prophase I : Homologous chromosomes pair up forming tetrads, while spindle fibers begin to form at opposite ends/”poles” of the cell. Metaphase I : As the spindle fibers fully develop they stretch out towards the center of the cell. The chromosomes of the cell move towards the metaphase plate (center of the cell). Anaphase I : The paired chromosomes divide into chromatids and begin to be pulled towards opposite poles of the cell by the spindle fibers. Telophase I : New nuclei form at the two ends of the cell with their corresponding chromosomes. The cell divides into two new daughter cells which then immediately begin Meiosis 2.

Meiosis Meiosis 2 Prophase II : The spindle fibers begin to reappear. Metaphase II : The chromosomes line up the the cells center. Each sister chromatids point toward the opposite poles its cell. Anaphase II : The sister chromatids are separated by the spindle fibers and move towards the opposite poles of the cell. Telophase II : The cells begin to divide once more and forming new distinct nuclei. Cytokinesis : The cells divide into four new daughter cells with half the number of chromosomes of the original parent cell.

Cell Cycle The cell cycle is is the life cycle of a cell and shows the “choices” the cell makes during its life. The cell cycle consists of an interphase state and a cell division state(ONLY mitosis is involved in the cell cycle since meiosis is not a cycle). Interphase G1 Phase : (Gap 1) In this gap the cell increases in size while producing RNA and protein. It also ensures the it is ready for DNA synthesis. S Phase : (Synthesis) A copy of the cells DNA is made in order to later on create two similar daughter cells. G2 Phase : (Gap 2) During this gap the cell continues to grow and produce protein. The cell then checks if it is ready to go into mitosis.

Cell Cycle Mitosis The cell undergoes mitosis and divides creating two new daughter cells. G0 Phase : (Gap 0) The cell will, at times, leave the cycle and stop duplicating. The cell does this to rest or stops permanently because it is at an end in its development.

Asexual Reproduction Sexual Reproduction The asexual form of reproduction is mitosis. Mitosis replicates a mother cell into two daughter cells which are identical. This is asexual reproduction because no other cell is needed in order to reproduce. The sexual form of reproduction is meiosis. Meiosis replicates the mother cell’s chromosomes into two daughter cells. Those cells then divide their chromosomes randomly into four new cells, creating cells similar to the mother cell but not identical.

Genetic Variation Genetic variation only occurs through meiosis, not mitosis. This is because mitosis involves the making of identical cells, while meiosis consists of factors like independent assortment and cross-overs. Independent assortment divides the chromosomes in cells randomly creating a varied result of sex cells. Cross-overs increase the varied factor.

Cancer Mutation in cells can cause their reproduction rate to go out of control. This mutation can comes from chemicals, radiation, or viruses. The rapid reproduction of cells creates tumors. Which then can lead to cancer unless the tumor is benign or non-invasive. Cancer is caused when the cells of tumors invade other neighboring tissues or enter the blood stream.