Cell cycle Flashcards
What is Interphase?
Interphase consists of G1, Synthesis, and G2 phases.
What occurs during G1 (Gap 1)?
Growth of the cell and checks of the DNA.
What occurs during Synthesis phase?
Duplication of chromosomes.
What occurs during G2 (Gap 2)?
Checks DNA synthesis completed properly and further growth.
What is Mitosis?
Mitosis is the process of cell division that includes Prophase, Prometaphase, Metaphase, Anaphase, Telophase, and Cytokinesis.
What happens during Prophase?
Condensing of chromosomes, formation of kinetochores, nuclear envelope breaks down, and mitotic spindle forms.
What happens during Prometaphase?
Duplicated chromosomes attach to the spindle.
What happens during Metaphase?
Chromosomes align at the cell equator.
What happens during Anaphase?
Sister chromatids separate and move towards the spindle poles.
What happens during Telophase?
Chromosomes decondense, nuclear envelope reforms, and spindle disappears.
What is Cytokinesis?
Physical separation into two new daughter cells at the end of mitosis.
What is G0 phase?
Resting phase, out of the cycle; differentiated cells are normally in G0.
What is Meiosis?
Meiosis involves DNA replication prior to meiosis I and results in four haploid nuclei.
What is the purpose of Meiosis?
Ensures the next generation has a diploid number of cells and a combination of traits different from either parent.
What occurs during Prophase 1 of Meiosis?
Dyad pairs align to create tetrads and crossing over occurs.
What occurs during Metaphase 1 of Meiosis?
Spindle fibers attach to dyad at kinetochore, aligning tetrads at the cell equator.
What occurs during Anaphase 1 of Meiosis?
Chiasmata break apart and sister chromatids migrate to opposite poles.
What occurs during Telophase 1 of Meiosis?
Cleavage furrow forms, initiating cytokinesis.
What is Interkinesis?
Rest period between meiosis 1 and meiosis 2.
What occurs during Meiosis 2?
Similar to mitosis but with only 23 chromosomes.
What are Cyclins?
Regulatory subunits governing progression of the cell cycle.
How many Cyclins are there?
There are 13+ cyclins.
How are Cyclins degraded?
Degraded via the ubiquitin/proteosome pathway.
What is the role of Cyclin D?
Promotes G0 to G1 transition and G1 progression.
What is the function of Cyclin E?
Initiation and progression of DNA replication.
What is the role of Cyclin A?
Initiation and progression of DNA replication.
What is the function of Cyclin B?
Entering mitosis and progression past anaphase.
What does Rb regulate?
Rb regulates the activity of TF E2F, which controls the expression of cyclins and genes needed in S phase.
What happens to Rb in the resting state (G1)?
Rb binds and inhibits E2F, blocking transactivation.
What is the effect of growth factor stimulus on Rb?
Stimulates expression of Cyclin D, which phosphorylates Rb and releases E2F.
What are Cyclin dependent kinases (CDKs)?
Enzymes that regulate the cell cycle by associating with cyclins.
What is the role of CDK inhibitors?
They bind to CDKs and interfere with their activity.
What is the significance of p21?
Inhibits virtually all CDKs and mediates G arrest in DNA damage.
What is the role of p27?
Implicated in G1 arrest and inhibits Rb phosphorylation.
What is the cell cycle in embryonic stem cells?
Greatly reduced time in G phase and increased time in S phase.
How do cyclins relate to cancer?
Cyclins can be overexpressed in cancers, leading to uncontrolled cell cycle progression.
What is the effect of recombinant adenovirus expressing p27?
Induces cell cycle arrest and loss of cyclin-CDK activity in breast cancer cells.
What is the role of chemotherapy in relation to CDKs?
Inhibition of CDKs leads to inhibition of cell cycle progression.
What are cell cycle checkpoints?
Defective in cancer cells, they can be targeted for treatment.
