Cell Division: the process of copying and dividing entire cells The cell grows, prepares for division, and then divides to form new daughter cells.

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1 Mitosis & Meiosis SC.912.L Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation.

2 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. Cell Division: the process of copying and dividing entire cells The cell grows, prepares for division, and then divides to form new daughter cells. Unicellular organisms allows duplicate using asexual reproduction Multicellular organisms allows to grow, develop from single cell to multicellular, makes other cells to repair and replace worn out cells Three types: binary fission (bacteria and fungi), mitosis, and meiosis

3 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. Cells divide through a process called the cell cycle which consists of interphase, mitosis, and cytokinesis. Note: majority of the cell cycle is Interphase, while a smaller portion is mitosis/cytokinesis.

4 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. Interphase: longest part of the cell cycle; growth, metabolism, and preparation for division occurs, duplicates chromosomes (DNA Replication)

5 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. MITOSIS division of nucleus of the cell Prophase: duplicated chromosomes and spindle fibers appear Metaphase: duplicated chromosomes line up randomly in center of cell between spindle fibers Anaphase: duplicated chromosomes pulled to opposite ends of cell Telophase: nuclear membrane forms around chromosomes at each end of the cell; spindle fibers disappear; chromosomes disperse

6 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. Cytokinesis: division of plasma membrane; two daughter cells result with exact genetic information In plants, a cell plate forms along the center and cuts the cell in half. In animals, a cleavage furrow develops to cut the cell in half.

7 1. Students will describe specific events occurring in each stage of the cell cycle and/or phases of mitosis, including cytokinesis. RESULTS OF MITOSIS: Two identical daughter cells Produces and occurs in somatic cells (body cells) Diploid = same number of chromosomes as original cell (humans = 46)

8 2. Students will explain how meiosis results in the formation of haploid gametes or spores. In meiosis, the cells will also start with interphase. There are TWO cell divisions instead of one, but the cell only does interphase ONCE prior to the first cell division. Meiosis is a reduction division process (chromosome numbers are divided in half) Each cell division consists of prophase, metaphase, anaphase, and telophase Occurs only in sex cells (gametes) and produces only gametes (egg and sperm)

9 2. Students will explain how meiosis results in the formation of haploid gametes or spores. First Division: Produces cells containing half # of double stranded chromosomes Prophase 1 crossing over occurs Metaphase 1 chromosomes line up in homologous pairs, independent assortment occurs Anaphase 1 chromosomes move towards each side Telophase 1 cells contain HALF of # of chromosomes

10 2. Students will explain how meiosis results in the formation of haploid gametes or spores. Crossing over: genes are essentially switching places on chromosomes in prophase I Independent assortment: the genes randomly move towards ends of cell in metaphase I THESE BOTH RESULT IN GENETIC VARIATION!

11 2. Students will explain how meiosis results in the formation of haploid gametes or spores. Second Division: Results in formation of four cells, each haploid (half the number of original chromosomes) (humans = 23)

12 2. Students will explain how meiosis results in the formation of haploid gametes or spores. RESULTS OF MEIOSIS: Four unique daughter cells Unique due to genetic variation such as crossing over and independent assortment Produces and occurs in gametes (sex cells) Haploid = half number of chromosomes as original cell (humans = 23) Sex cells combine during sexual reproduction to produce a diploid individual

13 3. Students will compare and contrast sexual and asexual reproduction. SEXUAL REPRODUCTION Pattern of reproduction that involves the production and fusion of haploid sex cells Haploid sperm from father fertilizes haploid egg from mother to make a diploid zygote

14 3. Students will compare and contrast sexual and asexual reproduction. ASEXUAL REPRODUCTION A single parent produces one or more identical offspring by dividing into two cells. Diploid cells are clones of parent cell.