Mitosis Meiosis CHAPTER 8 CHROMOSOMES n n Chromosome

Mitosis & Meiosis CHAPTER 8

CHROMOSOMES n n Chromosome: DNA in a Eukaryotic cell that is tightly coiled and compacted in the cell nucleus Histones: Proteins in Which DNA is Tightly wrapped Around that Help maintain The shape of The chromosomes

Chromosome Structure: n n Chromosome numbers: Chromosomes are categorized as either sex chromosomes or autosomes Sex chromosomes: chromosomes that determine the sex of an organism Autosomes: all other chromosomes in an organism

n Homologous chromosomes: one copy of each autosome from each parent. The two copies of each autosome are called homologous chromosomes Diploid: cells having 2 sets Of chromosomes n Haploid: cells which contain only one set of chromosomes n

Karyotype: photomicrograph of the chromosomes in a cell

Cell division in prokaryotes: Binary fission

Mitosis: n n If a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome). The copies then must be separated & sorted into two sides of the cell. The cell then splits in two. Part of each parent is carried to the two new cells. Results in cells such as internal organs, skin, bones, blood, etc.

Mitosis n Mitosis animations: n http: //www. youtube. com/watch? v=Vl. N 7 K 1 -9 QB 0

Interphase occurs just before Mitosis begins: Ø Cells spend most of the cell cycle in interphase Ø During g 1 – offspring cells grow to mature size Ø During S phasecells DNA is copied Ø During g 2 phasecell prepares for cell division (mitosis) http: //www. bioweb. uncc. edu/1110 Lab/notes 1/lab 6. htm

G 0 phase Cells can sometimes exit the cell cycle usually from the g 1 phase and enter s state called g 0 v During g 0, cells do not copy their DNA and do not prepare for cell division. v Many cells in the human body are in the g 0 phase v

Interphase Animal cell Plant cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

st 1 step in Mitosis: Prophase (preparation phase) The DNA recoils, and the chromosomes condense; the nuclear membrane disappears, and the mitotic spindles begin to form. http: //www. bioweb. uncc. edu/1110 Lab/notes 1/lab 6. htm

Mitosis Prophase Animal cell Plant cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

2 nd step in Mitosis: metaphase The chromosomes line up the middle of the cell with the help of spindle fibers attached to the centromere of each replicated chromosome. http: //www. bioweb. uncc. edu/1110 Lab/notes 1/lab 6. htm

Mitosis Metaphase Animal cell Plant cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

rd 3 step in Mitosis: Anaphase (separation phase) The chromosomes split in the middle and the sister chromatids are pulled by the spindle fibers to opposite poles of the cell. http: //www. bioweb. uncc. edu/1110 Lab/notes 1/lab 6. htm

Mitosis Anaphase Animal cell Plant cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

th 4 step in Mitosis: Telophase spindle fibers dissasemble, and the chromosomes return to a less condensed chromatin state. A nuclear envelope forms around each set of chromosomes and a nucleolus forms in each of the newly formed cells. http: //www. bioweb. uncc. edu/1110 Lab/notes 1/lab 6. htm

Mitosis Telophase Animal cell Plant cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

After Mitosis: Cytokinesis The actual splitting of the daughter cells into two separate cells is called cytokinesis and occurs differently in both plant and animal Cells. Beginning of cytokinesis in a plant: a plate forms along the midline of the dividing cell Beginning of cytokinesis in an animal: cell membrane pinches in at the middle of the dividing cell(this is called a cleavage furrow)

REMEMBER! Interphase Prophase Metaphase Anaphase Telophase Cytokinesis IPMATC http: //www. youtube. com/watch? v=L 0 kenzoe. OM Julie Camp’s mitosis power point - http: //sciencespot. net/Pages/classbio. html#Anchor-mitosis

Meiosis: n As in mitosis, if a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome). n Results in reproductive cells (sperm, eggs, etc). n Part of each parent is carried to the four new cells.

Meiosis Interphase The cell grows and copies its DNA, and the chromatin begins to condense into chromosomes. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Prophase I -DNA coils tightly into chromosomes and spindle fibers appear -In meiosis the homologous chromosomes pair with one another to form tetrads - Portions of chromatids may break off and attach to adjacent chromatids, this process is called crossing over. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Metaphase I - The tetrads line up randomly along the midline of the cell -Spindle fibers attach to the centromeres of each homologous chromosome http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Anaphase I -The chromosomes move to opposite ends of the cell. - The random separation of the homologous chromosomes is called independent assortment http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Telophase I & Cytokinesis The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Prophase II Spindle fibers form and begin moving chromosomes toward the middle of the cell http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Metaphase II As in Meiosis I, the chromosomes line up on the spindle fibers at the midline of the cell. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Meiosis Anaphase II The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell. http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

Telophase II & Cytokinesis - - a nuclear membrane forms around the chromosomes in each of the four new cells. Cytokinesis II then occurs. - each new cell contains half the original cells number of chromosomes http: //morgan. rutgers. edu/Morgan. Web. Frames/Level 1/Page 7/meiosis 1. html

http: //www. youtube. com/watch? v=z. GVBAH Asj. JM&feature=g-vrec http: //www. youtube. com/watch? v=q. CLm. R 9 -YY 7 o