Larry M. Frolich, Ph.D. Biology Department, Yavapai College Cell Metabolism and Mitosis Genetics ReviewGenetics Review ChromosomesChromosomes Mitosis—produces identical daughter cellsMitosis—produces identical daughter cells Meiosis—produces gametesMeiosis—produces gametes

Larry M. Frolich, Ph.D. Biology Department, Yavapai College GENETICS (the quick view—much more later) Cells divide and pass on instructions coded in DNA of chromosomes Each chromosome is a huge DNA molecule with coded information –DNA replicates to pass on information –DNA is transcribed to make proteins that run cell metabolism Cancer—example of what happens when genetic control goes awry Normal inheritance and meiosis

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM3 Chromosomes Karyotype: –ordered display of an individual’s chromosomes. –Collection of chromosomes from mitotic cells. –Staining can reveal visible band patterns, gross anomalies.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM4 Karyotyping

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM5

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM6

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM7

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM8 Homologues Chromosomes exist in homologous pairs in diploid cells. Exception: Sex chromosomes (X, Y). Other chromosomes are known as autosomes, they have homologues.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM9 In humans … 23 chromosomes donated by each parent (total = 46 or 23 pairs). Gametes (sperm/ova): –Contain 22 autosomes and 1 sex chromosome. –Are haploid (haploid number “n” = 23 in humans). Fertilization/syngamy results in zygote with 2 haploid sets of chromosomes - now diploid. –Diploid cell; 2n = 46. (n=23 in humans) Most cells in the body produced by mitosis. Only gametes are produced by meiosis.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM10 Chromosome numbers All are even numbers – diploid (2n) sets of homologous chromosomes! Ploidy = number of copies of each chromosome. Diploidy

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Mitosis—cell division Why do cells divide? –Growth—so tissues/structures can become larger –Replacement—many tissues are constantly being replaced because they get worn out or used up. E.g. blood, skin, lining of gut, sperm –Repair—when tissues get damaged due to injury

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Mitosis—what happens (overview) DNA/chrosomes replicate (make exact copies Copies line up at center of cell Copies pulled to opposite ends of cells by centromeres/spindles Cell membrane pinches off and splits cell into two

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Mitosis—details/stages 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Larry M. Frolich, Ph.D. Biology Department, Yavapai College 1. Mitosis: Prophase Chromosomes condense and become visible Nuclear envelope fragments Nucleolus disappears Centrosomes move to opposite poles Spindle fibers appear and attach to the centromere

Larry M. Frolich, Ph.D. Biology Department, Yavapai College 2. Mitosis: Metaphase Chromosomes line up at the middle of the cell (equator) Fully formed spindle

Larry M. Frolich, Ph.D. Biology Department, Yavapai College 3. Mitosis: Anaphase Sister chromatids separate at the centromeres and move towards the poles

Larry M. Frolich, Ph.D. Biology Department, Yavapai College 4. Mitosis:Telophase and cytokinesis Chromosomes arrive at the poles Chromosomes become indistinct chromatin again Nucleoli reappear Spindle disappears Nuclear envelope reassembles Two daughter cells are formed by a ring of actin filaments (cleavage furrow)

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Mitosis—constant, fast, keeps body functioning Remember, mitosis produces two identical daughter cells Mitosis is constantly happening in your body to allow for growth, replacement and repair While you read this slide, millions of new cells were produced by mitosis in the tissues of your body! Don’t forget cellular scale and intelligence— it’s a whole planet happening at the sub- microscopic level

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM19 Meiosis – key differences from mitosis Meiosis reduces the number of chromosomes by half. Daughter cells differ from parent, and each other. Meiosis involves two divisions, Mitosis only one. Meiosis I involves: –Synapsis – homologous chromosomes pair up. Chiasmata form (crossing over of non-sister chromatids). –In Metaphase I, homologous pairs line up at metaphase plate. –In Anaphase I, sister chromatids do NOT separate. –Overall, separation of homologous pairs of chromosomes, rather than sister chromatids of individual chromosome.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM20

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM21

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM22

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM23 Animation

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM24 Meiosis 1 First division of meiosis Prophase 1: Each chromosome dupicates and remains closely associated. These are called sister chromatids. Crossing-over can occur during the latter part of this stage.Crossing-over Metaphase 1: Homologous chromosomes align at the equatorial plate. Anaphase 1: Homologous pairs separate with sister chromatids remaining together. Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM25 Meiosis II Second division of meiosis: Gamete formation Prophase 2: DNA does not replicate. Metaphase 2: Chromosomes align at the equatorial plate. Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole. Telophase 2: Cell division is complete. Four haploid daughter cells are obtained.

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM26 Mitosis vs. meiosis

Larry M. Frolich, Ph.D. Biology Department, Yavapai College Meiosis KM27