Cell Cycle Regulation

Question 1

Define:

• cell proliferation:
• growth factor:
• transcription factor:
• cell signalling:
• cell cycle:

Answer 1

• cell proliferation: an increase in number of cells as a result of cell growth and division
• growth factor: polypeptides that control animal cell growth and differentiation, usually produced near where they act, can be stored and released by ECM
• transcription factor: a protein that regulates activity of RNA polymerase
• cell signalling: phosphorylation of residues
• cell cycle: how cells divide - reproduce by performing an orderly sequence of events in which it duplicates its contents and then divides in two

Question 2

What are the phases of the cell cycle?

How is it controlled?

Answer 2

• G1 (–>) G0

(checkpoint)

• S - DNA replication
• G2

(checkpoint)

• M - Mitosis

Controlled by cyclins and CDKs

• at beginning of G1, cyclin D phosphorylates pRb –> cyclin E at end of G1 phase
• cyclins and CDKs act in concert to move through cell cycle
• sometimes can be overexpressed or mutated –> unregulated cell growth

Question 3

Define mitosis:

What are the stages of the M phase?

Answer 3

Mitosis: the division of the nucleus of a eukaryotic cell, involving condensation of the DNA into visible chromosomes, and separation of duplicated chromosomes to form two identical sets

M phase: prophase, prometaphase, metaphase, anaphase, telophase

Question 4

Give an overview of what happens in M phase:

Answer 4

M phase:

• chromosome condensation
• formation of mitotic spindle
• attachment of chromosomes to spindle
• sister chromatids separate
• move to opposite poles of the spindle
• formation of new nuclei

Question 5

What happens at:

• prophase:
• prometaphase:
• metaphase:
• anaphase:
• telophase:

What is the next stage?

Answer 5

• prophase: duplicated chromosomes begin to form mitotic spindle, nuclear envelop still intact, chromosomes begin to condense
• prometaphase: nuclear envelop breaks down, chromosomes attach to spindles via kinetochores and undergo active movement to the equator
• metaphase: kinetochores attach sister chromatids to opposite poles of the spindle
• anaphase: sister chromatids separate to form daughter chromosomes, kinetochores get shorter and spindle poles move apart
• telophase: chromosomes arrive at poles and decondense, reformation of nuclear envelops

Cytokinesis: division of cytoplasm

Question 6

How is the cell cycle controlled?

Where are the checkpoints?

Answer 6

• timer
• events in correct order
• event take place only once per cycle
• on/off switch trigger events in a complete and irreversible fashion
• robustness
• adaptability

Checkpoints:

• G1 checkpoint - is environment favourable?
• G2 checkpoint - is all DNA replicated, is environment favourable?
• metaphase checkpoint - are all chromosomes attached to the spindle?

Question 7

Which hallmarks of cancer lead to cell cycle going on and on?

Answer 7

• sustaining proliferative signalling
• evading growth suppressors
• enabling replicative immortality

Question 8

What is genomics?

Genome?

Answer 8

Genomics: field of biology focusing on structure, function, evolution, mapping and editing of genomes.

A genome is an organisms complete set of DNA - it includes all the genes