2.8 Control of Cell Division

The 3 main processes of the cell cycle are…

Interphase, mitosis, and cytokinesis

What are stem cells (undifferentiated cells)?

The cells that undergo rapid cell division

What triggers a stem cell to divide?

Its size and signals from the environment (cell inhibition, growth hormones)

The cell cycle is important as it…

Allows certain processes to be switched on/off

6 cell cycle checkpoints:

G0, G1, S, G2, M, Cytokinesis

What occurs at the G0 checkpoint?

Cells are removed from the cycle and are still functioning

What occurs at the G1 checkpoint?

Cell growth starts, ribosome and protein synthesis occur

What occurs at the S checkpoint?

DNA replication, histone and phospholipid synthesis

What occurs at the G2 checkpoint?

Developing and preparing organelles for division

What occurs at the M checkpoint?

Mitosis and division of the nucleus

What occurs at the cytokinesis checkpoint?

Division of the cytoplasm and two new cells formed

What are cell checkpoints?

Points where the cell cycle is checked to make sure the cell is ready to continue further in the cycle and the essential processes and reactions have been carried out properly.

5 external factors controlling the cell cycle:

Growth factors, nutrient, anchorage and density dependence, and large cell size

3 Internal factor controlling the cell cycle:

Gene products, oncogenes and tumour suppressor genes

What do gene products do?

Regulate the cell cycle (e.g. cyclin)

How does cyclin work?

It binds with enzymes called Cdks, this actives the Cdks and forms mitosis promoting factors that help to initiate and regulate mitosis.

What are tumour suppressor genes?

p53 prevents production of cells with damaged DNA. If p53 isn't activated, unrepaired DNA can be passed on in the cell cycle.

What is cancer?

The uncontrolled division of cells, it appears in cancer cells with faulty checkpoints (p53).

3 things linked to cancer:

Chemical carcinogens, radiation and viruses

What are chemical carcinogens?

Cause changes in the nucleotide sequence of DNA (e.g. tobacco)

What is radiation?

Causes chromosome breaks (e.g. UV light)

What are viruses?

Causes an addition of foreign DNA sequences to the host's DNA

What is cell culturing?

The ability to grow cells successfully in a lab

5 conditions to culture cells:

A medium, nutrient source, optimum temperature, stable pH and sterile environment

3 examples of cell culturing:

Making insulin, yeast for bread and alcohol, and drug testing.

Cell culturing - 2 applications

Manufacturing vaccines and testing the effect of antibiotics on bacterial infections

Cell culturing - 2 limitations

Accumulation of toxins/dead cells and changes in pH of the growth media