Cell Cycle Flashcards
What is the purpose of the cell cycle?
duplication of identical cells; one cell divides into two
List 4 reasons why the cell cycle happens
- development: cells duplicate and can then differentiate (become other types of cells)
- wound healing: to replace damaged cells
- replacement of old or damaged cells
- pathological: cancer
3 different cell division rates between cell types
Most Neurons-don’t divide
Fibroblasts (part of skin)-can divide every 20 hours
Bone marrow cells-divide every 90.5 hours
G1 phase
first growth phase preparing for rest of the cell cycle,
makes sure the cell is big enough, has enough components.
during this phase the chromosomes only have one copy. Two homologous chromosomes one from dad and one from mom
G0 phase
cell cycle arrest
some cells can go from G0 into G1 but require an external signal to do so. Other cells never enter G1 because they don’t replicate. And other cells never STOP replicating so they’re NEVER in G0
S
duplication of chromosome into sister chromatids. Identical copies of the same chromosomes, held together by centromere
G2
synthesis of proteins required for mitosis
Interphase includes…
G1, S, G2
Mitosis
Is the actual replication of the chromosomes. What I ALWAYS had deemed was the cell cycle. It’s the process by which DNA is divided into 2 identical cells
Most cell growth occurs during…
G1 and G2 phases
Describe DNA packing during the cell cycle
- DNA has areas that are unwound so that transcription/translation can occur during growth phases
- all the DNA is unwound during S so that the DNA can be replicated
- Compared to mitosis where the DNA is mostly tightly packed
G1 checkpoint checks for what 4 things?
- Cell size
- Nutrients
- Growth factors
- DNA damage
G2 checkpoint checks for what 3 things?
- cell size-is the cell big enough?
- DNA replication-has it replicated?
- Is the DNA damaged?
What’s the most important checkpoint?
G1 TO S
How does the cell know that checkpoints have been reached?
- cellular signaling
- regulators of checkpoints
What times of cellular signaling helps the cell know the checkpoints have been reached?
External-growth signals that tell the cell to divide
Internal-that checks for things like DNA damage
What are the regulators of checkpoints?
Cyclin and CDK
Cyclin
protein regulator of CDK
CDK
is always present but not active most of the time, only active when cyclin is around, a protein that phosphorylates other proteins
Growth factors can stimulate…
the translation/transcription of a cyclin (generally for the G1 to S transition)
CDKs can turn cyclins from
inactive to active, and active to inactive
when CDKs are no longer needed they are
degraded by protosome
Cells said to be in the G0 stage are…
in an extended G1 phase and no longer cycling. They would require an external signal to be an active part of the cell cycle again
Cells in the G2 stage of the cell cycle have ____ as cells of the same species in the G1 stage
twice as many chromatids
A cell cycle ‘checkpoint’ would be best described as?
specific stages when further progress of the cell cycle can be halted
The cell is said to be committed to go through the cell cycle after it passes which of the following checkppoints?
G1 to S. this checkpoint commits the cell to the cell cycle after DNA has been replicated
The purpose of a cyclin is to
activate the kinase activity of CDK
