Mitosis and the Cell Cycle Mrs. Schenfield’s 8 th Grade Life Science

The Importance of Mitosis Growth and Repair Growth and Repair Reproduction of single celled organisms. Reproduction of single celled organisms.

The need to heal!

The need to grow!

Cell Cycle 95% of cell cycle in interphase 95% of cell cycle in interphase 5% of cell cycle in mitosis ending with cytokinesis. 5% of cell cycle in mitosis ending with cytokinesis.

Cell Cycle-Interphase (G1, S, G2) G1 = cell grows G1 = cell grows S = genes (DNA) duplicated S = genes (DNA) duplicated G2= Prepares to divide G2= Prepares to divide M= Mitosis-cell M= Mitosis-cell goes through prophase, metaphase, anaphase, and telophase. INTERPHASE “G1” or Growth 1 phase (Interphase) “S” or DNA Synthesis (Genes copied) G2 or Growth 2 phase-Prepares to become two cells. “M” or Mitosis phase

DNA Replication – Simple in Principle, Complicated in Practice How are genes duplicated? During the “S” period of interphase the DNA uncoils and an exact copy is made of each side. During the “S” period of interphase the DNA uncoils and an exact copy is made of each side.

DNA is Packaged into ChromosomesDNA is Packaged into Chromosomes DNA is packaged into chromosomes.

The Link Between DNA Replication and Chromosome Duplication

Chromosomes Chromosome- consists of two identical halves connected together by a centromere. Chromosome- consists of two identical halves connected together by a centromere. Chromatid- a half of one chromosome. Chromatid- a half of one chromosome. Contains one complete set of information Contains one complete set of information Copies itself to make the other chromatid Copies itself to make the other chromatid

DNA is Condensed into Visible Chromosomes Only For Brief Periods in the Life of a Cell 95% of the time, chromosomes are like this. Chromosomes can be seen 5% of the time in an actively growing cell and less in a non- growing cell.

Cell division requires coordinated division of chromosomes (mitosis) ….. …… and division of the cytoplasm (cytokinesis).

Stages of Mitosis Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase Cytokinesis Cytokinesis

Cancer Is One Outcome of A Runaway Cell Cycle Picture of prostate cancer cells during division.

The Knit of Identity - Mitosis Precisely and Evenly Divides Duplicated Chromosomes Dividing the duplicated chromosomes in the phases of mitosis provides each new cell with an identical and complete set of genes. interphase Prophase Metaphase The sister chromatids line up at the center of the spindle.

Mitosis Precisely and Evenly Divides Duplicated Chromosomes Cytokinesis is the process of cell division and it is distinct and separable from mitosis.

Mitosis in Action. Blue shows DNA, green shows spindle fibers. Interphase Early prophaseLate prophase Early metaphase MetaphaseEarly anaphaseLate anaphaseLate telophase

In Animal Cells, a Cleavage Furrow Forms and Separates Daughter Cells (Cytokinesis) Actual picture of a cell using an electron microscope. Cleave furrow in a dividing frog cell.

The Plant Cell Wall Forces Cytokinesis to Play by Different Rules

Use your notes to identify the stage of mitosis each cell is in. Cell #1 Cell #2

Stage? Cell #3 Cell #4

Stages? Cell #5 Cell #6

Stages? Cell #7 Cell #8