Dat Biology- Cell Division

Front 1

Prophase

Back 1

1. The nucleoli disappear and chromatin condenses into chromosomes.
2. Nuclear envelope breaks down.
3. The mitotic spindle is assembled and microtubules attach to the kinetochore region.

Front 2

Metaphase

Back 2

Begins when the chromosomes are lined up on the metaphase plate and ends when the microtubules (attached to kinetochores) pull each chromosome apart into two chromatids.

Front 3

Anaphase

Back 3

Begins after the chromosomes are separated into chromatids. The microtubules (now connected to chromosomes) shorten, pulling the chromosomes to opposite poles. At the end of anaphase, each pole has a complete set of chromosomes (the same number as the original cell).

Front 4

Telophase

Back 4

Concludes nuclear division. During this phase, a nuclear envelope develops around each pole, forming two nuclei. The chromosomes disperse into chromatin and the nucleoli reappear.

Front 5

Cytokinesis

Back 5

Divides the cytoplasm to form to separate cells. Different process in animals and plants- animals produce a cleavage furrow (outside in) and plant cells produce a cell plate (inside out).

Front 6

Growth

Back 6

After the completion of mitosis and cytokinesis, the cell begins a period of growth. Three phases- G1, S, and G2. It is during S phase that replication occurs.

Front 7

Meiosis

Back 7

Very similar to mitosis but there are two groups of divisions (meiosis I and meiosis II) and while the parent cell is 2n each daughter cell is just n.

Front 8

Prophase I

Back 8

Same as mitosis but homologous chromosomes pair (synapse). Corresponding regions along nonsister chromatids form close associations (chiasmata) and crossing over occurs.

Front 9

Metaphase I

Back 9

Homologous pairs align on the metaphase plate. Microtubules extend and attach to the kinetochore one member of each pair.

Front 10

Anaphase I

Back 10

Homologues within the tetrads uncouple as they are pulled to opposite poles.

Front 11

Telophase I

Back 11

The chromosomes have reached their respective poles and a nuclear membrane develops around them. Each pole will form a new nucleus that will have half of the number of chromosomes.

Front 12

Meiosis II

Back 12

Similar to mitosis. The end result is four haploid cells and each cell contains half the number of chromosomes. Each chromosome contains one chromatid.

Front 13

Genetic recombination

Back 13

Three causes: Crossing over, independent assortment of homologues, and random joining of gametes.

Front 14

Regulation of the cell cycle

Back 14

surface to volume ratio- when a cell grows, the volume increases faster than the surface area. Small surface areas cause the cell to stop growth and begin division.

Also, genome-to-volume ratio is used. The genetic material in the nucleus (genome) stays at a constant size even if the cell is growing.

Front 15

Checkpoints

Back 15

There are multiple checkpoints that the cell uses to evaluate internal and external conditions to determine if division should continue.

G1= occurs at the end of G1. Cell will enter G0 if it is determined that division should not go on.

G2= occurs at the end of G2 and evaluates the accuracy of DNA replication and signals whether or not to begin mitosis.

M checkpoint= occurs during metaphase, ensures that microtubules are appropriately attached to all kinetochores at teh metaphase plate before division (anaphase) continues.

Front 16

Cdk's

Back 16

Enzymes that activate proteins that regulate the cell cycle by attaching a phosphate group to them. Activated by cyclin, a protein that varies throughout the cell cycles.

Front 17

Growth factors

Back 17

The PM of cells have receptors for growth factors that stimulate division.

Front 18

Density dependent inhibition

Back 18

Many cells stop dividing when the surrounding cell density reaches a certain maximum level.

Front 19

Anchorage dependence

Back 19

Most cells only divide when they are attached to an external surface.