CBIO 3400 EXm #4

• What is G1 phase?

  Growth phase

  Cell grows in size, produces more organelles, mRNA, and proteins required for copying DNA.
• What is S phase?

  The period in which DNA is synthesized.
• Which transition marks the entry into the cell cycle?

  The G1 to S phase.
• What is the G2 phase?

  Final growth and prep stage. More proteins required for cell cycle are created.
• What is the M phase?

  Cell division

  Mitotic cell division
• What is the G0 phase?

  Cells do not cycle for an indefinite period of time. Can be reversible (quiescence) or irreversible (senescence).
• How much genetic material does a cell contain in the G1 phase?

  2n
• How much genetic material does a cell contain in the S phase?

  2n - 4n
• How much genetic material does a cell contain in the G2 phase?

  4n
• What is the order of the cell cycle?

  G1/ G0

  S

  G2

  M
• How much of the cell cycle does G1 make up?

  30-40%
• Describe the restriction point.

  G1/S checkpoint where DNA is checked for damage, ensures cell is the proper size, and that there are enough growth factors inn the cell environment.
• Describe how FACS (fluorescence activated cell sorting) can be used to determine DNA content using fluorescent DNA-binding dyes.

  1. Cells treated with fluorescent dye.

  2. Cells passed single-file through a column and excited.

  3. Intensity of light emitted corresponds to DNA content.
• What is the full name for CDK?

  Cyclin dependent kinase
• What is the role of CDK?

  CDK is a protein enzyme that regulates cell division via phosphorylation to activate or deactivate cellular processes BUT they require cyclin to work.

  CDK activity (CDK-cyclin) drives the cell cycle.
• What are cyclin?

  Activators of Cdk. Specific types of cyclin correspond to cell cycle stage specific.
• What type of cyclin and Cdks are present in the G1 phase?

  Cyclin D

  Cdk4, Cdk6
• What type of cyclin and Cdks are present in the G1/S phase?

  Cyclin E

  Cdk2
• What type of cyclin and Cdks are present in the S phase?

  Cyclin A

  Cdk2
• What type of cyclin and Cdks are present in the S/G2/M phase?

  Cyclin B, cyclin A

  Cdk1
• What does MPF stand for?

  Maturation promoting factors
• What is the role of MPFs?

  Promotes entry into the M phase via phosphorylation of various proteins.

  Composed of Cdk + cyclin.

  
  

  Diffusible factor that induces mitosis.
• What are some commonly used model organisms?

  Fruit flies (Drosophilia)

  C. elegans (roundworm)

  Mice

  Rats
• What are some common features shared by model organisms?

  Fast reproduction rate

  Short life span (able to study more generations)

  Relatively small

  Relatively similar to humans

  Ease of manipulation
• What does MPF activity depend on?

  The presence of cyclin B.
• The only mRNA that needs to be translated to activate cycling is the ___ mRNA.

  Cyclin B (mRNA encoding a nondegradable cyclin B).
• What are Cdcs?

  Cdc refers to a family of genes that encode proteins essential for various stages of the cell cycle in eukaryotes.
• What is the Wee1 mutation?

  A gene that encodes for the Wee1 kinase that inhibits Cdk1 by phosphorylating it thus regulating the G2/ M checkpoint.

  Recessive and multiple alleles that do varying things?
• What is the Wee2 mutation?

  Dominant, single allele.

  An allele of Cdc2. Mutation that changes Cdc2-Y15F causing Cdc2 kinase to be constitutively active.
• What is the inactive form of Cdc?

  Cdc2-P
• What is the active form of Cdc?

  Cdc2 and P-Cdc2
• What is Cdc25?

  A phosphatase that dephosphorylates Cdc2-P, turning it into Cdc2
• What are conditional mutants?

  Mutations carried in a genome that affects the phenotype only under certain circumstances.

  Permissive: regular phenotype

  Restrictive: mutation expressed
• What is Cdc2?


  A Cdk

  Group of proteins that regulate the cell cycle.
• Are the same type of cyclin used throughout the cell cycle?

  No, several distinct cyclins exist for distinct phases of the cell cycle.

  Distinct cyclin/ Cdk complexes have different substrates specificity to drive the specific phases of the cell cycle.
• What are the two regulatory sites of Cdk?

  Inhibitory: T14, Y15

  Activation: T160, T161
• What is the role of CAK?

  CDK-activating kinase; CAK is an kinase enzyme that activates Cdk.

  Cdc25-CAK work together to produce P-Cdc2
• How is Cdk activated?

  1. Cyclin binding

  2. Phosphorylation of Thr in the activated loop (=T loop) by CAK (requires phosphate to be completely active).
• How does the binding of cyclin change Cdk2 activity?

  When a cyclin binds to a specific binding site on the Cdk, it induces a conformational change in the Cdk protein. This change exposes the catalytic site of the Cdk, allowing it to bind to ATP.

  Partially active.
• How does the binding of phosphorous change Cdk2 activity?

  CAK phosphorylates the Thr160 residue in the activation loop that enhances Cdk activity.