Biology: Cell Cycle And Mitosis

Front 1

Cell Cycle: M Phase Events

Back 1

•Nuclear division occurs in four stages (prophase, anaphase, metaphase and telophase).

•This is followed by cytokinesis - division of the cytoplasm.

Front 2

Cell Cycle: M Phase Checkpoints

Back 2

•A checkpoint chemical triggers the condensation of chromatin.

•The metaphase checkpoint ensures that the cell is ready to complete mitosis.

Front 3

Cell Cycle: G1 Phase Events

Back 3

•Cells grow and increase in volume.

•Protein synthesis occurs to produce enzymes needed for S Phase.

•Organelles are replicated.

Front 4

Cell Cycle: G1 Phase Checkpoints

Back 4

•A G1 checkpoint control mechanism ensures that the chemicals needed for DNA replication are present and that the DNA is undamaged before entering the S-phase.

•The p53 gene also helps to control the G1 Phase.

Front 5

Cell Cycle: S-phase Events

Back 5

•DNA is replicated.

Front 6

Cell Cycle: S-phase Checkpoints

Back 6

•Once the cell enters the S-phase it is committed to completing the cell cycle.

•Genes active in all cell types are copies first.

•Genes usually inactive in specific cell types are copied last.

Front 7

Cell Cycle: G2 Phase Events

Back 7

•Cells continue to increase in volume.

Front 8

Cell Cycle: G2 Phase Checkpoints

Back 8

•The G2/M checkpoint ensures that the DNA has been replicated without errors before entering mitosis.

•Chemicals ensure the cell is ready to start mitosis by stimulating proteins that will be involved in chromosome condensation and spindle formation

Front 9

Mitosis and Meiosis Differences

Back 9

Mitosis:

•Necessary for growth and repair of tissues.

•1 division

•2 daughter cells formed.

•Results in genetically identical cells.

•Number of chromosomes stays the same.

•Produces diploid cells.

•Asexual reproduction.

Meiosis:

•Takes place in the reproductive organs to produce gametes.

•2 divisions

•4 daughter cells formed.

•Results in genetically different cells.

•Number of chromosomes is halved.

•Produces haploid cells.

•Sexual reproduction.

Front 10

Haploid

Back 10

Haploid - A cell or organims that has one copy of each chromosome.

Front 11

Diploid

Back 11

Diploid - cells or organisms that have two copies of each chromosome in their nuclei.

Front 12

Mitosis - Definition

Back 12

Mitosis is the process by which new body cells are produced for:

•Growth

•Replacing damaged or old cells and reparing tissues.

Front 13

Homologous Chromosomes

Back 13

Most cells of the body contain chromosomes in matching pairs that hold the same genes at the same positions along the chromosome. These pairs are called homologous chromosomes.

Front 14

Histone

Back 14

A protein that DNA is wrapped around to form chromatin.

Front 15

Chromatids

Back 15

The "arms" of a replicated chromosome.

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Centromere

Back 16

The area of a chromosome where two sister chromatids are joined together.

Front 17

Mitosis: Prophase

Back 17

•Chromosomes shorten and thicken by supercoiling to form sister chromatids. The chromosomes are now visible.

•The nuclear envelope breaks down.

•The centriole divides in two and the two centrioles move to opposite poles of the cell.

•Spindle fibres are formed between the two centrioles from a cytoskeleton protein called tubulin.

Front 18

Mitosis: Metaphase

Back 18

•Chromosomes move to the equator of the cell.

•Chromosomes attach to the spindle by their centromeres.

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Mitosis: Anaphase

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•Centromere splits.

•The spindle shortens, pulling sister chromatids in opposite directions towards the poles of the cell.

Front 20

Mitosis: Telophase

Back 20

•Chromatids reach the poles of the cell.

•New nuclear envelope forms around each set.

•Spindle breaks down.

•Chromosomes uncoil and become invisible again.

Front 21

Cytokinesis

Back 21

•Occurs after mitosis.

•The cytoplasm and organelles are divided into two and the cell splits to form two daughter cells.