Cell Cycle

Chromosomes Compact, coiled DNA Chromatid Centromere One half of the chromosome Centromere Between the two chromatids holds them together

Number of Chromosomes Humans have 46 chromosomes 2 are sex chromosomes 44 are autosomes

Types of chromosomes Sex chromosomes Autosomes Chromosomes that determine the sex of an organism Humans have an X or Y chromosome Male: XY Female: XX Autosomes All other chromosomes in an organism

Homologous Chromosomes There are only 23 different chromosomes To have 46 we have two copies of each chromosome We get one from our mom and one from our dad The pairs of each chromosome are called homologues Homologues are the same size, shape, and carry the same genes

Karyotype Show’s the 23 pairs of chromosomes 22 homologous pairs of autosomes 1 pair of sex chromosomes

Diploid & Haploid Diploid (2n) Haploid (n) Cells that have 2 sets of chromosomes All cells, other than reproductive cells, are diploid Haploid (n) Cells that have only 1 set of chromosomes Reproductive cells (sperm & eggs) are haploid

Cell Division All cells come from preexisting cells Prokaryotes Binary Fission Eukaryotes Mitosis Meiosis

Binary Fission The chromosome makes a copy of itself The cell grows until it reaches about 2x it’s size A cell wall forms between the two chromosomes and the cell splits

Mitosis How all cells divide EXCEPT reproductive cells The cytoplasm and nucleus both divide Results in two cells that are genetically identical

Mitosis – Cell Cycle Interphase Cell Division Time between cell divisions Cell Division Time when the cell is dividing

INTERPHASE G1 phase S phase G2 phase Grow to mature size DNA is copied Prepares for cell division

Mitosis - Prophase DNA is shortened and tightened into chromosomes Nucleolus & nuclear membrane break down & disappear Two centrosomes appear Animals also have centrioles Centrosomes move to opposite poles of cell Spindle fibers radiate from centrosomes

Mitosis - Metaphase Spindle fibers move chromosomes to the center of cell

Mitosis - Anaphase Chromatids separate at the centromere and are pulled to opposite poles of cell by spindle fibers

Mitosis - Telophase Spindle fibers break down Chromosome loosens up Nuclear envelope forms around each set of chromosomes Cleavage furrow forms Nucleolus forms

Cytokinesis Cell membrane pinches inward creating a cleavage furrow Eventually leads to two cells

Cell Plate Only in plants Makes a cell wall