Cell Cycle and Mitosis

Why do Cells Divide? For repair of cells in case of an injury Growth and development Produce Reproductive cells

Chromosome & DNA Chromosomes are wrapped up DNA

Structure of a chromosome Structure of a chromosome Gene – segment of DNA that codes for a specific Protein Chromosomes – Wrapped up DNA Chromatids – two exact copies of DNA Centromere - Center point of the chromosome attaching the two chromatids. Centromere Chromatids

Karyotypes Two Types of Chromosomes Sex Chromosomes Determines male or female XX = female XY = male Autosomal Chromosomes Rest of the cells that do not determine the sex

Karyotype Video Click Here! Karyotype Project

Chromosome Numbers in Different Species

Cell Cycle

Basically represent the “life of a Eukaryotic cell”

Cell Cycle Includes… Interphase (“inter-” between) G ◦ G 1 - First Growth Phase (46 strands of DNA)  Carries out normal functions  Becomes less efficient as it gets bigger S ◦ S - DNA Synthesis Phase (92 strands of DNA)  DNA is copied to make an exact duplicate G ◦ G 2 - Second Growth Phase (92 strands of DNA  Continual Cell Growth Mitosis (Occurs in every cell except sex cells) ◦ Stages where a cell divides Cytokinesis ◦ Splitting of the Cytoplasm & Cell Membrane

Cell Cycle Animation Click Here!

Cell Cycle “Check Points” “Check Points” – make a decision on whether conditions are favorable to move on to the next stage.

Problems with Checkpoints can lead to cancer. cancer Cancer is uncontrolled growth of abnormal cells.

Helpful Terminology Diploid (2N) Both DNA strands from mom and dad Haploid (1N) Half the DNA strands of a normal cell ◦ Mixture of mom and dad’s DNA

Mitosis v. Meiosis MitosisMeiosis Occurs in normal cells Produces genetically identical cells Starts with a Diploid cell and produces Diploid cells Starts with one cell and produces two cells Occurs in Sex Cells (or reproductive) Produces genetically different cells called gametes (Sperm or Eggs) Starts with a Diploid cell and produces Haploid cells Starts with one cell and produces four cells

Meiosis (Not Mitosis) We all started our life out as a zygote (2N) After that we developed by undergoing mitotic divisions

Mitosis How a cell divides Biology Mr. Gorby

IPMATI I Pee Monday And Thursday I Pee Monday And Thursday Interphase between replication phase (“Inter-” means between) Phases of Mitosis ◦ Prophase ◦ Metaphase ◦ Anaphase ◦ Telophase

DNA coils & condenses into chromosomes Centromeres show up Nuclear Membrane Disappears Microtubles, called spindle fibers, (Little fingers) extend out from the centrioles and attach to centromeres Why does the nuclear envelope have to disappear? Prophase Prophase What Happens? Prophase

Microtubles – called “Spindle Fibers”

Metaphase Metaphase What happens? Metaphase Microtubles push the chromosome to the center to line the chromosomes up at the metaphase plate (in the center) Why does this happen? Click on Picture for Animation

Anaphase Centromeres split and chromatids are each pulled to either side of the cell Telophase Microtubles dissappear Nuclear envelope reappears Centromeres dissappear DNA uncoils AnaphaseAnaphase & Telophase What happens? Telophase AnaphaseTelophase

Cytokenesis What happens? Cell splits into two daughter cells Each cell Begins Interphase over again What does the term “daughter cells” mean?

Mitosis The overall picture

Remembering Where Mitosis Takes Place “My-toe-sis” Mitosis occurs in all cells except “sex cells” ◦ Purpose = growth and repair A cell division called meiosis occurs in Sex Cells ◦ Purpose = Reproduction of organism