Topic 1.4 - Cell cycle regulation

Question 1

What are the three cell cycle check points and their purposes ?

Answer 1

G1 checkpoint
* Monitors potential growth conditions (nutrients, etc.)
* Assesses level of DNA damage (from UV, etc.)
G2 checkpoint
* Monitors state of pre-mitotic cell (suitable size, etc.)
* Identifies and repairs any DNA replication errors
Metaphase checkpoint
* Ensures proper alignment (prevents aneuploidy)

Question 2

What are cyclins ?

Answer 2

Cyclins are proteins that control progression of the cell cycle

Question 3

Give the purposes of cyclins

Answer 3

Cyclins bind to cyclin dependent kinases (CDKs)
The activated complex phosphorylates proteins involved
in specific cell cycle events (e.g. centrosome duplication)
After the event has occurred, the cyclin is degraded and
the cyclin dependent kinase is rendered inactive

Question 4

How are cancers caused ?

Answer 4

They are caused by uncontrollable cell division

Question 5

What is the result of uncontrolled cell division ?

Answer 5

Abnormal growths called tumours

Question 6

What are the two types of tumours ?

Answer 6

Tumor cells may remain in their original location (benign) or spread and invade neighbouring tissues (malignant)

Question 7

What is metastasis ?

Answer 7

Metastasis is the spread of cancer from an original site to a new body location (forming a secondary tumor)

Question 8

Cite the two main factors of cancer origins

Answer 8

Mutagens and genetics

Question 9

How can mutagens cause cancer ?

Answer 9

Mutagens are agents that change the genetic material of cells
* These agents may be either physical (e.g. UV), chemical
(e.g. arsenic) or biological in origin (e.g. certain viruses)
* Mutagens that cause cancer are classified as carcinogens

Question 10

How can genetics cause cancer ?

Answer 10

Most cancers are caused by mutations to two classes of genes:
* Proto-oncogenes stimulate cell growth and proliferation
* Tumor suppressor genes repress cell cycle progression
Proto-oncogene mutations create cancer-causing oncogenes

Question 11

How is cell death caused ?

Answer 11

Necrosis (uncontrolled ‘cell homicide’) and Apoptosis (programmed ‘cell suicide’)

Question 12

What is necrosis ?

Answer 12

The cell loses functional control due to injury, toxins, etc.
* There is a destabilization of the membranes, leading to swelling
* The cell bursts and releases its contents (causing inflammation)

Question 13

What is apoptosis ?

Answer 13

It is a controlled event triggered by mitochondrial proteins
* Cell contents are packaged in membranous protrusions (blebs)
* The cell fragments into apoptotic bodies which are recycled