CH 10.6: Control of the Cell Cycle Flashcards
What are the 2 Irreversible steps of the Cell Cycle?
- DNA replication
- The separation of the sister chromatids during anaphase
What is MPF?
- Mitosis Promoting Factor
- Cyclin + cdc2 (Kinase)
What are the 2 key aspects of MPF?
- It’s activity follows cyclin activity= Increasing going into mitosis & decreasing coming out
- The enzymic activity of MPF involves the phosphorylation of proteins
What is the protein encoded by the cdc2 gene?
-Kinase
What role do the cdk Enzymes play?
-They are the engine that drives cell division
What are the 3 checkpoints of the Cell Cycle?
- G1/S
- G2/M
- late Metaphase (the spindle checkpoint)
What is the purpose of having checkpoints?
- It allows the cycle to be delayed/ halted when necessary (nutrient deficiency or damage detected)
- It assesses internal state & integrates external signals
What is the purpose of the G1/S checkpoint?
- AKA Restriction point!
- It is the primary point at which the cell decides to divide or not= external signals can influence events of the cell cycle
What is the purpose of the G2/M checkpoint?
- It represents the commitment to Mitosis
- It examines the success of DNA replication & can stop if the replication is wack
- It also examines the balance of kinase that adds inhibitory phosphates w/ the phosphatase that removes them
What is the purpose of the late Metaphase checkpoint?
- It is the spindle checkpoint
- Ensures that all the chromosomes are attached to the spindle in preparation for anaphase & making sure that they are arranged on the metaphase plate
What is the primary mech of Cell Cycle control?
-Phosphorylation to amino acids serine, threonine, tyrosine in proteins
What is APC?
-Anaphase promoting complex
What are the 2 main purposes of APC in Mitosis?
- To trigger anaphase itself by
- Activating separase that removes the cohesins holding the sister chromatids together
- Necessary for destruction of mitotic cyclins to drive cells out of mitosis
How does APC mark proteins for destruction?
-By the Proteosome= organelle responsible for the controlled degradation of proteins
What is the signal to degrade a protein?
- Ubiquitin
- SO APC acts as ubiquitin ligase
What are the differences between complex animals & single-celled eukaryotes in terms of cdk & signals acted on the cell?
- Multiple cdks control the cycle vs 1 cdk in yeasts
- Animals cells respond to more external signals vs yeast bc yeasts are horny & only respond to those
How are cells able to sense the density of the cell culture around them?
-When cells touch, receptor proteins in plasma membrane activate a signal transduction pathway that acts to inhibit cdk action= prevents entry to cell cycle
How do Growth Factors act?
-They trigger intracellular signaling systems
What is the passage through the checkpoints controlled by?
-The cdk enzymes
If the gene encoding one of the proteins mutated so that it could not perform its normal function, what would be the consequences?
- The chromosomes aren’t able to condense
- The chromosomes would not be able to properly align at the metaphase plate
- Separation of sister chromatids would not likely occur during anaphase A
- The nuclear envelope would not be able to form
What is true about Mitosis & Cytokinesis?
-At the end of cytokinesis there are 2 daughter cells w/ a normal complement of diploid genetic material
What happens to the microtubules that are attached and unattached to the chromosomes during anaphase?
-The microtubules attached to the chromosomes are gonna shorten while the microtubules that aren’t attached are gonna elongate as the cell expands
What happens if Cohesin failed to degrade during metaphase/anaphase transition?
-The daughter cells wouldn’t have a complete set of chromosomes & there would be 2 copies of the chromosomes present
What is true about the human somatic cell that is in G2 about their chromosomal number & structure?
- The cells would be considered Haploid, Diploid, Tetraploid
- They would also be aligned in the middle of the cell
In what phase is the success of DNA replication examined?
-G2 phase
At what phase would the cell w/ a low pH NOT pass the checkpoint?
-G1 phase
