Cell Cycle

Question 1

What are 4 stages for cell cycle?

Answer 1

Prophase, prometaphase, metaphase, anaphase + telophase

Question 2

What happens in prophase?

Answer 2

Chromosomes condense
Centromere move to opposite poles
Mitotic spindle forms

Question 3

What happens in prometaphase?

Answer 3

Breakdown of nuclear envelope

Chromosomes attach to mitotic spindle

Question 4

What happens in metaphase ?

Answer 4

Centrosome are at opposite poles

Chromosomes are at their most condensed + line up at equator of mitotic spindle

Question 5

What happens in anaphase?

Answer 5

Sister chromatids separate synchronously

Each new daughter chromosomes moving to opposite spindle poles

Question 6

What happens in telophase?

Answer 6

Chromosome arrives at spindle poles
Chromosomes decondense
Nuclear envelope reforms

Question 7

What are 3 types of spindle microtubules?

Answer 7

Astral
Kinetochore
Interpolar

Question 8

What is definition of kinetochore?

Answer 8

Protein structure formed on chromatid where spindle fibres attach to pull

Question 9

What is centromere?

Answer 9

Part of chromosome connected to spindle fibre

Question 10

What is definition of chromatids?

Answer 10

2 chromosomes that have been replicated + linked through centromere

Question 11

What is definition of cytokinesis?

Answer 11

Divides cytoplasm into 2 daughter cells

At position of metaphase plane

Question 12

What is mitotic spindle?

Answer 12

Bipolar array of microtubules=> + end=growing end, - end= shrinking end
Start to assemble during prophase from centrosomes at each pole
Attach to chromosomes via kinetochore
Pull apart sister chromatids

Question 13

What is composed of contractile ring?

Answer 13

Is composed of actin + myosin II outside the cell into 2 daughter cells
Accumulates between poles of mitotic spindle beneath plasma membrane
Ring contracts + forms cleavage furrow => dividing cell in two

Question 14

What is centrosome?

Answer 14

Is where microtubules assemble

Question 15

What is meiosis?

Answer 15

Specialised cell division that starts with one diploid cells + ends with 4 haploid cells

Question 16

What occurs in meiosis I?

Answer 16

Homologous chromosomes line up on spindle + separate to opposite poles

Question 17

What occurs in meiosis II?

Answer 17

Sister chromatids line up on spindle + separate to opposite spindle pole

Question 18

When meiosis goes wrong, it is called

Answer 18

Non disjunction

Question 19

Regulation of cell cycle

Answer 19

Entry into cell cycle must be strictly controlled
Each phase must occur only once per cell cycle
Phases must be in correct order: G1-S-G2-M
Phases must be non-overlapping

Question 20

What are 3 checkpoints?

Answer 20

G1 checkpoint=> check extracellular environment, check DNA for damage
G2 checkpoint=> check DNA replicated properly, check DNA for damage
Metaphase checkpoint=> are all chromosomes aligned on mitotic spindle

Question 21

What are cell cycle regulators?

Answer 21

Cyclin dependent kinases (Cdk)=> enzymes that phosphorylate target proteins. Become active when bound to corresponding cyclin
Cyclins=> regulators of Cdks. Different cyclins are produced at each phase of cell cycle

Question 22

Cell cycle control in Yeast

Answer 22

Single Cdk binds successively to different cyclins

Cdk binding to S cyclin triggers S phase

Question 23

Cell cycle control in humans

Answer 23

Different classes of Cdk + cyclins act at each stage of cell cycle
Cyclin 1=> ensures DNA replication occurs properly

Question 24

What are 2 families of cyclin dependent kinase inhibitors?

Answer 24

Inhibitor of kinase 4 family (INK4)=> inhibit G1 CDKs
CDK inhibitory protein/ kinase inhibitor protein (CIP/KIP)=> inhibit all other CDK-cyclin complexes gradually sequestered by G1 CDKs thus allowing activation of later CDKs

Question 25

Cell cycle + cancer

Answer 25

Neoplasia
Mis regulation of cell cycle causes cancer
Cells escape normal cell cycle checkpoint=> uncontrolled progression through cell cycle
Many genes that regulate cell cycle (p53,pRB) are often mutated in human cancers