cell cycle

Question 1

explain the what happens to cohesins when microtubules bind to centromeres

Answer 1

cyclins break down along the length of the chromosome apart from at the centromere

these cohesins break down last to prevent aneuploidy

Question 2

name some cohesinopathies

Answer 2

Roberts syndrome
Conerlia de Lange syndrome
Non-disjunction of chromosomes

Question 3

what are CDKs?

Answer 3

cyclin dependent kinases - regulate progression of the cell cycle

Question 4

what activates CDKs?

Answer 4

cyclins

Question 5

what does the retinoblastoma protein do?

Answer 5

inhibits E2F proteins by binding to them

stops cells from going past G1 into S phase

Question 6

what happens when Cdk2 is activated?

Answer 6

inactivates Rb by phosphorylation so E2F is released so the cell can enter S phase

Question 7

explain the role of p53 in controlling the progression of the cell cycle

Answer 7

p53 is a transcription factor
binds to the gene for p21
p21 controls whether or not cyclin-Cdk2 can activate E2F by phosphorylating Rb

Question 8

how does the mutation of the RB1 protein lead to cancer?

Answer 8

mutation means no functional Rb
no Rb binds to E2F
E2F doesnt stop cell from entering S phase
uncontrolled proliferation –> cancer

Question 9

what are the three cell cycle checkpoints?

Answer 9

end of G1
G2-M transition
Mitosis (metaphase)

Question 10

what happens at the end of G1 checkpoint?

Answer 10

checks cell size, growth factors and DNA damage

controlled by p16 which inhibits CDK 4/6 so it cant interact with cyclin D

Question 11

what happens in the G2-M checkpoint?

Answer 11

checks DNA replication, damage and cell size

stops cell cycle if there’s damage

Question 12

what happens in the mitosis checkpoint?

Answer 12

checks that the chromosomes are attached to the spindles

Question 13

what are the three main types of chemotherapy?

Answer 13

anti-mitotics
biologics
antihormonal drugs

Question 14

what are the two classes of anti-mitotics?

Answer 14

vinca-alkaloids

taxanes

Question 15

what do vinca alkaloids do?

Answer 15

prevent microtubule formation

metaphase cannot occur

Question 16

what do taxanes do?

Answer 16

prevent the microtubule disassembly

cells cant enter telophase

Question 17

what are biologics?

Answer 17

monoclonal antibodies

Question 18

when are anti-hormonal chemotherapies used for?

Answer 18

hormone driven cancers

caused by overexpression of a receptor or sensitive to a hormone

Question 19

what stages form interphase?

Answer 19

g1
s
g2

Question 20

what happens during G1 and G2?

Answer 20

no DNA synthesis

environment is monitored

Question 21

what happens in G1?

Answer 21

Monitors internal and external environmental conditions to ensure it is suitable for mitosis.

Question 22

what happens in G2?

Answer 22

double checks DNA has been copied properly. Any mistakes are repaired, if they are unable to be repaired the cell undergoes apoptosis

Question 23

what happens in S phase?

Answer 23

DNA replication

2n to 4n

Question 24

what are the stages of mitosis?

Answer 24

o	Prophase
o	Metaphase
o	Anaphase
o	Telophase 
o	Cytokinesis

Question 25

what happens in prophase?

Answer 25

- DNA condenses into visible chromosomes - nucleoli disappears - nuclear membrane breaks down - chromosomes join at the centromeres - centrioles move to the poles in pairs - microtubules radiate and attach to chromosomes

Question 26

what is the kinetochore?

Answer 26

how microtubules attach to the centromere of a chromosome

Question 27

describe the structure of the kinetochore

Answer 27

inner region - binds to centrosome (present throughout cell cycle) outer region - interacts with microtubules (made during cell division)

Question 28

what happens during metaphase?

Answer 28

* Kinetochore / microtubules are used to pull chromosomes apart – one from each pair of sister chromatids pulled towards opposite ends * Chromosomes line up in the middle * Centrosomes are at the polar ends of the cell

Question 29

what happens in anaphase?

Answer 29

* Sister chromatids are separated by the microtubules * Chromatids are pulled to polar ends * When chromosome reaches centrosome the poles separate further by elongation of the polar microtubules

Question 30

what is cohesin?

Answer 30

a protein to hold sister chromatids together

Question 31

what is aneuploidy?

Answer 31

presence of abnormal number of chromosomes

Question 32

how can aneuploidy occur?

Answer 32

if kinetochore doesnt attach to the microtubules properly so the sister chromatids dont separate if cohesin doesnt break down so the chromatids dont separate

Question 33

what happens in telophase?

Answer 33

- chromosomes arrive at polar ends - uncoiling of chromosomes - nuclear envelope reforms - cell's pinched until it cleaves and forms 2 daughter cells

Question 34

what happens in cytokinesis?

Answer 34

* Cytoplasm splits between the 2 cells | * Cell divides

Question 35

what is the purpose of meiosis?

Answer 35

specialised cell division to make gametes

Question 36

when does recombination occur?

Answer 36

prometaphase I of meiosis

Question 37

what happens in prophase I?

Answer 37

Recombination/crossing over. o Microtubules and proteins extend across the cell. Membrane around the nucleus of the cell erodes and the chromosomes are set free

Question 38

what happens in metaphase I?

Answer 38

Chromosome pairs line up. Random assortment

Question 39

what happens in anaphase I?

Answer 39

spindles pull chromosome pairs apart

Question 40

what happens in telophase I?

Answer 40

Chromosomes finishing moving to their opposite poles

Question 41

what happens in prophase II?

Answer 41

Chromosomes condense, forming an X structure. Membrane around nucleus dissolves and chromosomes are released. Centrioles duplicate and meiotic spindle is formed.

Question 42

what happens in metaphase 2?

Answer 42

- Chromosomes line up. - Centrioles are located at the poles of the cell. - Meiotic spindle attaches itself to each of the chromatids.

Question 43

what happens in anaphase 2?

Answer 43

chromatids are split and divided and pulled to the two opposite poles of the cell

Question 44

what happens in telophase 2?

Answer 44

Same as telophase I with the addition of cytokinesis, resulting in four gametes with distinct genetic information. Chromosomes finish moving to the poles