Mol Lecture #19

Question 1

Anaphase

Answer 1

• Separase (protein) releases the sister chromatids by cleaving cohesins (at this point, they are now called daughter chromosomes)
• Daughter chromosomes move along the kinetochore microtubules
• Non-kinetochore microtubules slide in opposing directions to push the two ends of the cells father apart.

Question 2

Telophase

Answer 2

• Putting the cells back together in an interphase state.
• Undoing the events of prophase and Prometaphase
  → chromosomes uncondensed
  → reform the nuclear envelope
  → disassemble the mitotic spindle

Question 3

Cytokinesis

Answer 3

• Microfilament structure pinches daughter cells apart along the former spindle midpoint.
• Make sure that everything is equally distributed
  Getting the DNA to each side is the most important aspect along the lines of equally distributing.

Question 4

Regulation of the Cell Cycle: What does it entail? What could happen?

Answer 4

• Cell division is closely tied to the need of the organism
• Constantly replacing things (ex. Lining of the intestinal tract)
• Ex. Increase in the amount of the production of red blood cells
• When this doesn’t go correctly it could lead to cancer or inflammation

Question 5

G1phase + Every other part of the cycle

Answer 5

• Do we want to divide or not
• Have we done the last step correctly

Question 6

Cell Cycle checkpoints

Answer 6

• Multiple points during which the cell takes stock of itself and its surroundings to determine if the cell cycle should proceed. Think of these points where ‘brakes’ might be applied. ‘Passing’ the checkpoint allows the next phase to proceed.
• G1/S checkpoint
• G2/M checkpoint
• Mitotic Spindle Checkpoint

Question 7

G1/S checkpoint

Answer 7

• Check to see if there’s anything wrong with the cell. See if the organism wants new cells (needs of the organism)

Question 8

G2/M checkpoint

Answer 8

• Check to see if the DNA was copied correctly. Check to see if there’s anything else wrong with the cell that would prevent moving forward.

Question 9

Mitotic Spindle Checkpoint

Answer 9

• make sure that the chromosomes are aligned correctly (metaphase to anaphase checkpoint)

Question 10

Molecular regulation of the cell cycle: Involves 2 components

Answer 10

Cyclins and CDKs

Question 11

Cyclin-dependent kinase (CdK’s):

Answer 11

• enzymes that activate downstream targets by phosphorylating them. (covalently add a phosphate group onto the protein, which activates the downstream proteins (the proteins breaking down the nuclear envelope, etc.))
  → CdK’s change activity during the cell cycle

Question 12

Cyclin:

Answer 12

-proteins that change in amount during the cell cycle. Control the activity of the CdKs by interacting with them

Question 13

G1/S cyclin:

Answer 13

• binds to CdK2 during G1 (Target: DNA polymerase- phosphorylates DNA to prepare it for DNA replication)

Question 14

S cyclin:

Answer 14

• binds CdK2 during S-phase to initiate DNA replication

Question 15

M cyclin:

Answer 15

• binds to CdK1 in G2 to stimulate mitosis. (phosphorylates nuclear lamins)

Question 16

Mechanisms of Regulation

Answer 16

• M cyclin will take the whole gap phase to produce an effect.

Question 17

Cyclins and CdKs

Answer 17

• Timeline of cyclin production
• The dramatic drops in the amount of cyclins are also regulated
• The cyclins are changing in amount of cell cycles, while CdKs are changing in amount of activity.

Question 18

Big picture of Cyclins and CdKs

Answer 18

Big picture: Gene regulation mirroring (transcriptional level, post-transcriptional level, and protein expression…)

Question 19

Cell Cycle is coordinated with activities of the organism

Answer 19

• Positively and negatively influence the cell cycle
• Stimulation of cell division by a growth factor
• Inhibition

Question 20

Growth factor

Answer 20

• growth factors enact signal transduction pathways to tell a cell to divide
• involves a protein

Question 21

Inhibition Factor

Answer 21

• growth inhibiting factors stop the cell from dividing, it causes the increase in gene expression of factors that inhibit cell division
  → one of those factors is contact inhibition: when cells touch, it often inhibits cell cycle progression
• involves a protein

Question 22

Cancer

Answer 22

• A collection of multiple diseases with similar genetic causes and phenotypic changes in cells affecting multiple tissues
• Cancers are genetic diseases (genetic basis) resulting in the loss of regulation of normal cell biology to give rise to abnormal cells

Question 23

Two main characteristics of cancer cells:

Answer 23

1) Unregulated cell division, no longer tied to the needs of the organism
2) Cancer cells invade and colonize other tissues

Question 24

Multistep progression of cancer

Answer 24

• Multistep process that requires multiple genetic alterations. These genetic changes impact cell cycle controls and the cell’s ability to be regulated by the organism’s needs.

Question 25

Multistep progression of cancer (ex. Colon Cancer)

Answer 25

• You need multiple changes from a normal colon cell to a cancerous one.
• Two base changes and the additional changes in the behavior of the cells along with a loss of a gene.
• Variability in mutations acquired (tumor growth, etc.)

Question 26

Mutations in Cancer: 2 types of mutations

Answer 26

• Gain of function mutations in proto-oncogenes
• Loss of function mutations

Question 27

Gain of function

Answer 27

Genes that usually stimulate the cell cycle- gas pedal of the cell cycle- to make them oncogenes (turning those genes on)

Question 28

Loss of function mutation

Answer 28

• Tumor suppressors (genes that generally inhibit the cell cycle- brake pedal) (turning these off)

Question 29

Mutations affecting cell cycle in cancer

Answer 29

• Genes that affect G1 cyclin might be changed
• Telomerase- can be considered a proto-oncogene