Unit 9: Cellular Growth Control Flashcards
What is the cell cycle?
A series of tightly regulated events that include interphase and mitosis in which a cell grows, replicates it’s DNA, and divides into two genetically identical daughter cells.
What are the steps of interphase?
G1, S, G2
Mitosis occupies a very short cycle in what cell type?
Somatic cells
What is the importance of checkpoints in a cell cycle?
They ensure appropriate progression through cell cycle
What is the first step in progression of a cell through the cell cycle?
Cyclin-dependent kinases (CDK’s) are activated by binding to cyclin proteins
The levels of what proteins oscillate throughout the cell cycle?
Cyclin
What cyclin promotes entry into mitosis and how?
Cyclin B binds to CDK1
How are CDK fully activated?
By cyclins AND other steps such as phosphorylation by other kinases (CDK activating kinases/ CAKs)
What is Proteolysis?
Degradation of specific proteins which regulate cell cycle progression
What triggers Proteolysis?
Ubiquitin
When a cell is ubiquitinated, what happens?
It is targeted by a proteosome which chews up and degrades proteins.
What does the anaphase promoting complex/cyclosome (APC/C) do?
Adds ubiquitin to specific cellular targets.
What is another name for Ubiquitin ligase?
Anaphase promoting complex/cyclosome
When a cell is ready to leave mitosis, what happens?
M phase cyclins are ubiquitinated and degraded by a proteosome.
When the cyclins are degraded, they can no longer activate M phase CDK’s and dephosphorylate CDK substrates.
How were cell cycle genes largely identified?
In budding yeast
Why is accurate replication of a genome important for a cell?
Prevents disease
What is a situation in which a cell has the wrong number of chromosomes?
Aneuploidy
At what step of the cell cycle is the genome copied?
S phase
What happens when a genome is copied and is ready to move on to the next step?
The origin of replication bound Origin Recognition complex (ORC) recruits MCM helicase to DNA.
What do S phase CDK’s activate?
Activate DNA-bound MCM helicase
What does DNA-bound MCM helicase do?
Activates helicase and promotes recruitment of DNA Polymerase
What does DNA polymerase do?
Copies DNA
When replication begins, what stops any additional rounds of replication from occuring?
The phosphorylation of the ORC which prevents the recruitment of additional MCM helicases
When are ORC’s phosphorylated and therefore inactive?
During replication up until mitotic exit when the APC/C inactivates the CDKs (by degrading M phase cyclins)
What is chromatin
Mixture of DNA and DNA binding proteins
What wraps DNA into a compact structure?
Nucleosomes
What links replicated sister chromatids together?
Cohesin
How do microtubules connect to the chromosomes?
kinetochores
