Cell Cycle

Question 1

Prophase

Answer 1

condensation of chromosomes; breakdown
of nuclear membrane; formation of mitotic spindle;
attachment of spindle fibers to kinetochores of
chromosomes

Question 2

Metaphase

Answer 2

lining up of chromosomes on metaphase

plate

Question 3

Anaphase

Answer 3

separation of sister chromatids of each
chromosome & their movement to spindle poles;
beginning of cytokinesis.

Question 4

Telophase

Answer 4

reformation of the nuclei (& nuclear
membrane); decondensation of chromosomes;
completion of cytokinesis

Question 5

Are 1st and 2nd meiotic division reductional or equatorial?

Answer 5

1st is reductional and 2nd is equatorial

Question 6

When do crossover events occur?

Answer 6

prophase I

Question 7

Number of chromosomes and amount of DNA at the end of 1st division

Answer 7

chromo: 1n and DNA is 2d

Question 8

Number of chromosomes and amount of DNA at the end of 2st division

Answer 8

chromo: 1n and DNA 1d

Question 9

how many phases of the cell cycle can be seen in LM?

Answer 9

2: interphase and division

Question 10

how many phases does cell cycle have?

Answer 10

4: G1, S, G2, M

Question 11

What happens in G1 phase?

Answer 11

period of normal cell growth and metabolism

Question 12

What happens in S phase?

Answer 12

DNA synthesis

Question 13

What happens in G2 phase?

Answer 13

synthesis of proteins and factors necessary for cell division

Question 14

What happens in M phase?

Answer 14

cell division and cytokinesis

Question 15

Describe G0 phase

Answer 15

adult cells that divide occasionally, undergo limited growth and active metabolism, to divide need to be stimulated by factors such as growth factors

Question 16

Describe Gtd phase?

Answer 16

terminally differentiated cells

Question 17

Cells in Gtd phase?

Answer 17

cardiac muscle cells and neurons

Question 18

Cells in G0 phase?

Answer 18

kidney cells, liver cells, and lung cells

Question 19

How do cells escape G0 phase?

Answer 19

stimulant such as Growth Factor

Question 20

Where is the passage of G0 phase to divisional cycle controlled at? Germ cells?

Answer 20

restriction point at G1 phase and for germ cells there is a 2nd restriction point in G2 which require proper hormonal stimulation to enter meiosis

Question 21

Define restriction points

Answer 21

control points in cycle under the influence of extracellular signals

Question 22

Define check points

Answer 22

control point in cycle that monitor DNA damage, proper DNA replication, proper alignment of chromosomes, etc. to ensure proper replication of undamaged genes to daughter cels

Question 23

What two fammilies of molecules control restriction and check points?

Answer 23

Cdks and cyclins

Question 24

What are the Cdk-cyclin complexes for G1-S?

Answer 24

Cyclin D- Cdk4/6 and Cyclin E-Cdk2`

Question 25

What is the Cdk-cyclin complex for S?

Answer 25

Cyclin A-Cdk2

Question 26

What is the Cdk-cyclin comples for S-G2?

Answer 26

Cyclin A-Cdk1

Question 27

What is the Cdk-cyclin complex for M?

Answer 27

Cyclin E-Cdk1

Question 28

Describe the 4 major ways in which the specificity of a Cdk is regulated?

Answer 28

- particular cyclin bound to it - activation by phosphorylation at Threonine near position 160 - inactivation by phosphorylation at Threonine 14 and Tyrosine 15 - interactions with Cdk inhibitor CKI

Question 29

Describe the process of Cyclin D exerting its effects

Answer 29

Cyclin D is synthesized in response to growth factors and binds Cdk4 and Cdk 6. Cyclin D/Cdk4 phosphorylate pRb t up to 16 sites allowing release of E2F. E2F turns on the transcription of genes for S phase.

Question 30

What molecule is necessary to bypass G1 restriction point?

Answer 30

Cyclin D

Question 31

Where does pRb bind E2F?

Answer 31

E2F is a TF and pRb binds it at promotes gene regions

Question 32

Is pRb phosphorylated when binding E2F?

Answer 32

No, phosphorylation causes release

Question 33

What CKI blocks progression through G1 restriction point? How?

Answer 33

p16, by bining to Cyclin D/Cdk4 complex

Question 34

Describe effects of Adenovirus E1A in Rb-E2F complex?

Answer 34

competes with E2F for binding to Rb thus blocking its normal binding to Rb.

Question 35

Describe effects of human papillomavirus in Rb-E2F complex?

Answer 35

encoded E7 induces degradation of Rb through the ubiquitin-proteasome pathway.

Question 36

Describe effects of SV40 T Antigen in Rb-E2F complex?

Answer 36

directly disrupts Rb-E2F complexes.

Question 37

When is p53 activated and what is its immediate effect?

Answer 37

activated by DNA damage and causes transcription of p21

Question 38

What are the overall effects of p53? What happens if DNA cannot be repaired?

Answer 38

blocks progression of cell cycle and cell division until DNA is repaired, if it cant then accumulated p53 will initiate apoptosis

Question 39

What is the function of p21?

Answer 39

it is ta general inhibitor of a number of Cdk.cyclin complexes and also blocks a cofactor of DNA pol (PCNA)`

Question 40

What determines wether apoptosis occurs?

Answer 40

it is a balance between pro-apoptotic and anti-apoptotic factors

Question 41

Which family of proteins are among the most potent apoptosis regulators?

Answer 41

Bcl-2 family (anti and pro apoptotic)

Question 42

What molecule binds p53 to inactivate it?

Answer 42

mdm2

Question 43

What are the microscopic events normally observed un apoptosis?

Answer 43

DNA fragmentation, chromatin condensation, fragmentation of nucleus, and fragmentation of the cell

Question 44

Describe the difference between necrosis and apoptosis

Answer 44

necrosis: cellular contents and degradative enzymes often spill out into surrounding tissue causing inflammation... apoptosis: remain intact and are destroyed cleanly by macrophages

Question 45

Describe the common conserved pathway of apoptosis:

Answer 45

- Proteins that promote apoptosis are induced - Endonucleases fragment and destroy nucleus - Cyto C and other apoptosis inducing factors from mitochondria are released - Cyto C activates caspase proteases in cytoplasm - Proteases destroy the cell

Question 46

What molecule is among the most potent of apoptosis inducing factors?

Answer 46

Cyto C

Question 47

Caspase proteases are members of what protein family?

Answer 47

ICE family of cystein proteases

Question 48

How does radiation therapy for cancer work?

Answer 48

Radiation therapy and many of drugs for cancer therapy involve induction of damage in DNA of cancer cell. P53 blocks the cell cycle until the DNA is repaired, and if it cannot be repaired induces death of the cell by apoptosis.

Question 49

Why are some cancer cells resistant to radiation therapy?

Answer 49

because they have loos or mutation in p53