Finals

Question 1

Senescent cells

Answer 1

A G0 state in which cells are not able to divide anymore by reaching their limit. Older cells, replicated a lot and can’t do it anymore.

Question 2

Quiescent cells

Answer 2

In G0 state where they are resting but can still go back to G1

Question 3

Differentiated cells

Answer 3

Cells in G0 state that are terminally differentiated cells. Specialized to the point where reproduction is no longer an option.

Question 4

Pulverization

Answer 4

Pulverization (grinding, cutting) of chromosome is found in S phase chromosomes when S phase and Mitotic cells are fused.

Question 5

Maturation-promoting factor (MPF)

Answer 5

Contain two components:

1) Serine/threonine kinase - phosphorylates
2) cyclin

These two components form a dimer when close to M phase, and together they make the MPF and allow entry into mitosis and helps regulate it.

In yeast cells, cdc2 kinase, cyclin, and phosphorylated Thr161 (reissue on kinase) complex is the MPF.

Question 6

Cyclin-dependent kinases (Cdks)

Answer 6

MPF-like enzymes. They help orchestrate what goes in inside cells at different points in cell cycle by phosphorylating the kinases and target the right targets and turns things on and allow things to progress in cells.

Question 7

Cdc2

Answer 7

In yeast, it’s the S/T kinase. Binds with G1/S cyclins to allow into S phase. Binds with mitotic cyclins in G2 to allow into M phase.

Progression through fission yeast cell cycle requires phosphorylation-dephosphorylation of critical cdc2 residues.

Question 8

CAK

Answer 8

Phosphorylates cdc2 on Threonine161 in G2.

Question 9

Wee 1

Answer 9

Phosphorylates cdc2 on tyrosine15 in G2. Without it, the cell will go thru G2 quickly and the cell that hasn’t grown to the sufficient size will divide and yield in two smaller cells named wee cells.

Question 10

Tyrosine 15

Answer 10

It’s phosphorylation inhibits action of threonine161 phosphorylation

Question 11

Threonine 161

Answer 11

Its phosphorylation is required for yeast cell to undergo mitosis. Its activity is inhibited by Tyr15 phosphorylation

Question 12

Cdc25

Answer 12

If everything is fine within the yeast cell, This phosphotase acts on Tyr15 to erase the phosphorylation. Without cdc25, cells will grow but will not go thru mitosis.

Question 13

Controlled proteolysis

Answer 13

Ubiquitin-proteasome system. It regulates concentrations of cyclins and other key cell cycle proteins by adjusting the rate of synthesis and rate of destruction of the molecules at different points in cell cycle.

Question 14

Subcellular localization

Answer 14

Dynamic phenomenon in which cell cycle regulators are moved into different compartments at different stages. Ex: cyclin B1 shuttles between nucleus and cytoplasm until G2, when it accumulates in the nucleus just prior to onset of mitosis. Cyclin B1 has a nuclear localization sequence that is phosphorylated and blocks the export of it from the nucleus.

Question 15

Combinations of cyclins and Cdks at different stages in mammalian cell cycle

Answer 15

Cdk4/6 + cyclin D = G1
Cdk2 + cyclin E = entry into S
Cdk2 + cyclin A = through S phase
Cdk1 + cyclin B/A = MPF

Question 16

Cdk inhibitors

Answer 16

p27, inhibitor of cyclin A-Cdk2, and must be degraded before entry into S.

Question 17

Prophase

Answer 17

Chromosomes form - protein scaffold gives the shape of the chromosome
Cytoskeleton disassembles
Mitotic spindle forms
Nuclear membrane dissolves
ER/Golgi fragment.

Question 18

Cohesin

Answer 18

Holds sister chromatids together. It is dissociated by phosphorylation during prophase except for at the centromere where it is unphosphorylated.

Question 19

Condensin

Answer 19

Multi protein complex that is responsible for compaction. It replaces cohesin in prophase by dissociating cohesin with polo-like kinase (PLk) and Aurora B kinase

Question 20

Centromere

Answer 20

Highly repeated DNA sequences allow specific protein binding.

Question 21

Kinetochore

Answer 21

Sits atop the centromere, has 100+ proteins.
Attachment to microtubules of mitotic spindle
Home to motor proteins for chromosome mobility
Mitotic checkpoint signaling component site.
Plus end of microtubules are adjacent to it.

Question 22

Mitotic spindle

Answer 22

Replicated during S phase.
During mitosis, they separate into two so each cell gets 2 centrioles.
Mammary cancer cells can contain multiple centrosomes.

Question 23

Prometaphase

Answer 23

Marked by:
Mitotic spindle fully assembled
Sister chromatids line-up at center

Question 24

Metaphase

Answer 24

Loss and addition of subunits is a dynamic process at the kinetochore
Sister chromatids are ready to separate

Question 25

Anaphase

Answer 25

Pulling apart happens

Anaphase A: sister chromatids pull apart
Anaphase B: mitotic spindles pull apart

Question 26

Spindle assembly checkpoint (SAC)

Answer 26

Needed to go to Anaphase
Assures metaphase plate
Activation induces delay of anaphase entry

Question 27

Anaphase promoting complex (APC)

Answer 27

Along with SCF complex, ubiquitinate substrates, leading to their destruction by proteasomes.

Question 28

APC(Cdc20)

Answer 28

Targets anaphase inhibitor securin (secures attachment of sister chromatids ).

Question 29

APC(Cdh-1)

Answer 29

Targets mitotic cyclins near the end of Mitosis, targets cyclin B (part of MPF).

Question 30

Telophase

Answer 30

Daughter cells start to return to interphase

Question 31

Abscission

Answer 31

Mammalian cells undergoing the final stage in cytokinesis.

Question 32

Midbody

Answer 32

What’s left of the mitotic spindle central body of the mother cell in between the two newly formed cell.

Question 33

Cytokinesis

Answer 33

Breaking of two daughter cells.
Actin filament ring interspersed with bipolar myosin filament forms and the ring contracts and forms cleavage furrow then it pinches off the daughter cells.