Basic Cell Biology Topic 3202C, 3025G, 3025H Melinda Klockziem Mitosis and Meiosis Basic Cell Biology Topic 3202C, 3025G, 3025H Melinda Klockziem

Mitosis

How do cells reproduce? Mitosis -- the cells divide to produce two identical cells. Genetic material in both is identical End up with two diploid cells Mitosis is necessary for growth and maintenance.

Stages of mitosis 1. Interphase The cell doubles its DNA Nucleoli and nuclear membrane present http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

http://www.bioweb.uncc.edu/biol1110/Stages.htm

Stages of mitosis 2. Prophase Sister Chromatids shorten and thicken Chromosomes visible Nuclear membrane disappears Chromosomes have “X” shape joined at the centromere http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

http://www.bioweb.uncc.edu/biol1110/Stages.htm

Stages of mitosis 3. Metaphase Sister chromatids line up along equator of the cell Attach to spindle fibers which act a guide to separate the sister chromatids http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

http://www.bioweb.uncc.edu/biol1110/Stages.htm

Stages of mitosis 4. Anaphase Sister chromatids separate Sister chromatids move to opposite ends of the cell http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

http://www.bioweb.uncc.edu/biol1110/Stages.htm

Stages of mitosis 5. Telophase Nuclear membranes reform Two new cells are separated Cytokinesis occurs http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

http://www.bioweb.uncc.edu/biol1110/Stages.htm

Animation of Mitosis Cell Alive Website

Cancer and Mitosis Mitosis is necessary, but… Uncontrolled mitosis is cancer. Cancer cells divide without control. Cancer cells create a mass in tissues or organs. Two types of Cancer Benign Malignant

Mitosis Yarn Lab

Meiosis

Background Information Chromosome Numbers Haploid or N Humans 23 Haploid number (N) Chromosomes are in pairs Humans have a total of 46 chromosomes or 2N (diploid) Meiosis reduces 2N to N Thus when sperm and ova meet and combine at fertilization the resulting embryo will have 2N

How else do cells reproduce? Meiosis is the reproduction of animal sex cells Ova and sperm Happens in two stages Two divisions of the cell compared to only one division in mitosis End up with four haploid cells

Stages of Meiosis I Prophase I Chromosomes thicken and becomes visible Chromosomes are present in homologous pairs http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis I Metaphase I Homologous pairs line up on the axis of the dividing cell opposite from each other. http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis I Anaphase I Homologous pairs of chromosomes leave each other and are pulled towards opposite poles by spindle fibers http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis I Telophase I The cells physically divide Each daughter cell now contains one chromosome from each pair Reduction Division Number of chromosomes is reduced from diploid to haploid. http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis II Prophase II Chromosomes still duplicated http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis II Metaphase II Sister chromatids line up on the axis of the cell. http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis II Anaphase II The sister chromatids are pulled apart at the centromere by spindle fiber http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html

Stages of Meiosis II Telophase II Nuclear membrane reforms Each of the four final haploid cells or gametes contain one strand from the original homologous pair of chromosomes. http://www.erin.utoronto.ca/~w3bio380/Lectsked/Supple2/meiosis.html