FoB lecture 15 - cell cycle control

What is the purpose of regulating the cell cycle?

To ensure there are enough resources for cells and to prevent cancer from mutations in DNA.

What are the key checkpoints in the cell cycle?

G1 Checkpoint, G2 Checkpoint, and Metaphase Checkpoint.

What must be checked at the G1 Checkpoint?

1. Cell size

2. nutrient sufficiency

3. social signals are present

4. DNA is undamaged

why is it important for a cell to get checked before dividing?

- if a cell with a bad mutation continues to divide, the news cells will inherit that mutation

- maintaining specific cell density ensures organisms can keep up with resource demands

*PROCESS for cyclin

when cyclij is made, it binds to CDK

↓

the CDK will start adding phospo groups to different proteins

↓

activating them making the proteins that are needed for the next phase

what 2 things are needed to pass G1 checkpoint?

Cyclin & E2F proteins

How do mutations contribute to cancer?

Mutations can lead to unchecked cell proliferation, evasion of cell death, and increased genome instability.

S-phase protein examples

DNA polymerase, primase, topoisomerase

What is the role of P53 proteins in the cell cycle?

- P53 proteins signal to stop cell division if DNA damage is present

- is able to activate a CDK inhibitor & stop the cell cycle

How do telomeres protect DNA during cell division?

- Telomeres act as a buffer for chromosomes, preventing the loss of protein-coding DNA during replication

- sequences of DNA that is capping the ends of every single chromosome

What happens if telomeres become too short?

Cells will no longer pass the G1 checkpoint, leading to cell senescence or death.

What is the Hayflick limit?

The average number of times a normal human cell population will divide before becoming senescent.

What is the function of telomerase?

- Telomerase restores telomere length, maintaining the replicative capacity of cells

- can bind to the end of the DNA strand

- can use itself as a template

What is the significance of the G2 Checkpoint?

It checks if DNA has been successfully replicated and if chromosomes are undamaged.

What does the Metaphase Checkpoint assess?

It checks if chromosomes are correctly attached to the spindle apparatus and properly segregated.

What is the role of cyclins in the cell cycle?

Cyclins activate CDKs, which are necessary for passing checkpoints and progressing through the cell cycle.

What is the BRCA1 gene's function in cancer prevention?

The BRCA1 gene encodes a protein that fixes DNA damage; mutations increase the risk of cancer.

What is the impact of UV radiation, X-rays, chemicals on DNA?

these can cause changes to DNA, which may lead to cancer if not repaired.

What are some treatments for cancer that target DNA synthesis?

Quinolones inhibit topoisomerase, and Taxol destabilizes microtubules to stop cell division.

What is the significance of cell density in relation to the cell cycle?

Maintaining specific cell density ensures that the organism can meet resource demands.

What happens if a cell with a mutation divides?

All new cells derived from that cell will inherit the mutation.

What is nucleotide excision repair?

- A DNA repair mechanism that fixes damage caused by mutagens.

- chop out the specific area thats not acting the way we want it to and we insert new nucleic bases

What is the relationship between telomere shortening and species lifespan?

The rate of telomere shortening can predict the lifespan of a species.

What role do growth factors play in the cell cycle?

Growth factors promote cell division by signaling cells to progress through the cycle.

What is the consequence of having extra copies of the P53 gene, as seen in elephants?

It increases the likelihood of triggering cell death in response to DNA damage.

What is the function of mismatch repair proteins?

They recognize and correct mismatches in DNA during replication.

What is the role of CDK in the cell cycle?

CDK is a protein that, when activated by cyclins, drives the cell cycle forward.

How does cancer affect the normal cell cycle?

Cancer cells proliferate unchecked and can evade programmed cell death.

What is the significance of social signals at the G1 checkpoint?

Social signals indicate whether the environment supports new cell growth.

What is the relationship between cell division and resource availability?

New cells must be supported by the environment to ensure viability and function.

What is checked at cell cycle checkpoints?

Cell cycle checkpoints check for DNA damage, proper DNA replication, and ensure that the cell is ready to proceed to the next phase.

Why are cell cycle checkpoints important?

They prevent the division of damaged or unprepared cells, which can lead to cancer and other diseases.

What mechanism is used at cell cycle checkpoints to regulate progression?

Checkpoints use cyclins and cyclin-dependent kinases (CDKs) to monitor and regulate the cell cycle.

What is the problem with lagging strand synthesis?

Lagging strand synthesis involves the formation of Okazaki fragments, which requires primase to create RNA primers, and is limited by the directionality of DNA polymerase.

How do telomeres protect chromosomes?

Telomeres protect chromosome ends from degradation and prevent loss of important DNA during replication.

What role does telomerase play in protecting DNA?

Telomerase adds repetitive nucleotide sequences to the ends of chromosomes, allowing for continued replication and preventing shortening.

What feature of telomerase allows it to elongate DNA ends?

Telomerase contains an RNA template that it uses to extend the telomeres, a function that DNA polymerase cannot perform.

What strategies do cancer cells use against the host organism?

Cancer cells can evade the immune system, promote angiogenesis, and manipulate normal cellular processes to support their growth.

Why do older animals have higher cancer rates than younger ones?

Older animals accumulate more mutations over time and have a decreased ability to repair DNA, leading to a higher incidence of cancer.

How does DNA polymerase correct errors?

DNA polymerase has proofreading ability, using exonuclease activity to remove incorrectly paired nucleotides during DNA synthesis.

What is mismatch repair?

Mismatch repair is a process that corrects errors that escape proofreading by DNA polymerase, ensuring fidelity in DNA replication.

What is nucleotide excision repair?

Nucleotide excision repair is a mechanism that removes damaged DNA segments and replaces them with correctly paired nucleotides.

what is MPF

- the name of the active cyclin-CDK complex that initiates mitosis or M-phase

- M phase promoting factor

whats the relationship between MPF activity & cyclin?

MPF activity increases as cell makes more cyclin