Cell Cycle and Checkpoints of Cell Division Flashcards
What are the four reasons to produce new cells?
- Duplicate DNA and segregate copies into daughter cells
- Replace old cells
- Repair injury
- Build new tissue
What typically occurs with cell cycle regulation? What happens if there is failure of cell cycle regulation?
Normally, if there is damage in a mother cell, the DNA repair pathway is signaled and the cell cycle will be stopped (cell division stops until DNA is repaired)
- If there is cell cycle regulation failure, some cells will undergo apoptosis but others will continue with the cell cycle and ultimately produce mutant daughter cells from the damaged mother cell
What is the role of the BRCA gene? What is the result of a mutation in the BRCA gene?
BRCA gene produces proteins involved in DNA repair
- If there is a mutation in the BRCA gene, the production of other genes that perform DNA repair will not occur, resulting in increased risk for breast or ovarian cancer
What are the four phases of the cell cycle? Describe each
- G1: duplication - all non-chromosomal cellular contents are duplicated
- S: synthesis/replication - each of the 46 chromosomes are duplicated
- G2: proofread/repair - cell double checks the duplicated chromosomes for any errors and repairs are made, if needed
- Mitosis: division - duplicated chromosomal DNA condenses into mitotic chromosomes
What are the five stages of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What is the final phase of the cell cycle (hint: sort of part of mitosis)? What happens in this phase?
Cytokinesis: the mitotic cells are divided into two daughter cells
How does the cell cycle begin? What does this step result in?
Mitogen (ligand) binds to their receptors on the cell surface, initiating a phosphorylation cascade
What gene and cascade are typically involved with the cell cycle initiation?
Ras gene and the MAP Kinase cascade
What are two results of the MAP Kinase cascade?
- MAP Kinase increases synthesis and activity of the MYC transcription factor
- MYC increases the expression of the cyclin D
What is required for the progression through checkpoints of the cell cycle? How is this process achieved (hint: complex)?
Progression through checkpoints requires phosphorylation of key proteins
- Phosphorylation is achieved by cyclin-CDK complexes
What are cyclins, and how are they regulated? How is cyclin synthesis regulated, and what is the one exception?
Cyclins are the regulatory subunit that bind to CDKs, ensuring that only proteins relevant to a specific cell cycle phase are phosphorylated
- Besides cyclin D, cyclin synthesis is initiated by preceding phase’s signaling event
How is cyclin D synthesis regulated?
Cyclin D is the only cyclin that’s synthesis is dependent upon
What does CDK stand for? How are they activated, and what is their role in the cell cycle when active?
Cyclin-dependent kinases (CDKs) are the “master switches” that regulate each phase of the cell cycle
- Always present in cells, but only active when bound to cyclin
What is always the first active cyclin-CDK complex of the cell cycle?
Cyclin D-CDK4/CDK6
What are the cyclin-CDK complexes for each phase (hint: there are 5)
- G1 (early): cyclin D-CDK4/CDK6
- G1 (late): cyclin E-CDK 2
- G1/S: cyclin A-CDK 2
- S/G2: cyclin A-CDK 1
- M: cyclin B-CDK 1