Cell cycle

Question 1

What phases are part of interphase?

Answer 1

G1
S
G2

Question 2

What phases are part of mitosis?

Answer 2

Prophase
Metaphase
Anaphase
Telophase

Question 3

What causes M arrest?

Answer 3

Improper spindle formation/ chromatids not correctly attached

Question 4

What causes G1 arrest?

Answer 4

DNA damage detected by p53 protein

Question 5

What causes S arrest?

Answer 5

Unreplicated DNA

Question 6

What causes G2 arrest?

Answer 6

DNA damage

Question 7

What’s euchromatin?

Answer 7

DNA with open conformation, unwound & active (appears light on transmission electron micrographs)

Question 8

What is heterochromatin?

Answer 8

Condensed & transcriptionally inactive DNA (appears dark on transmission electron micrographs)

Question 9

Name the 2 qualities necessary to be identified as a stem cell

Answer 9

ability to self renew

potency/ ability to differentiate into different cell types

Question 10

Cells capable of forming all differentiated cells of an adult

Answer 10

Totipotent (total - all)

Question 11

Cells capable of forming more than 1 differenitated cell type

Answer 11

Pluripotent (plural - many)

Question 12

What type of cells are present in the inner cell mass of blastocyst?

Answer 12

Totipotent cells

Question 13

2 types of cloning

Answer 13

therapeutic - cells from early embryo transferred to culture dish
reproductive - embryo placed into a foster mother

Question 14

What type of cells are present in a developing embryo?

Answer 14

Pluripotent cells that can develop into any functional cells type

Question 15

What cells are present in adult that can develop into a restricted set of different cell types?

Answer 15

multi potent cells

Question 16

What are committed progenitor cells?

Answer 16

Cells that serve to generate only 1 cell type e.g. epidermal stem cell
Also known as unipotent stem cells

Question 17

What does the adult stem cell plasticity concept suggest?

Answer 17

certain multipotent stem cells can become pluripotent given the correct environment

Question 18

What 2 stem cells do bone marrow contain?

Answer 18

Haematopoietic stem cells

Bone marrow stomal/ mesenchymal stem cells

Question 19

What do haematopoietic stem cells give rise to? What type of stem cells are they?

Answer 19

Pluripotent

All of the types of blood cells

Question 20

What do bone marrow stomal/ mesenchymal stem cells give rise to?

Answer 20

Bone 
Cartilage
Fat
Cells that support the formation of blood
Fibrous connective tissue

Question 21

What name is given to proteins that are released by cells with specific effect on cell interaction/ communication/ behaviour?

Answer 21

Cytokines

Question 22

Examples of cytokines

Answer 22

Interleukins
Lymphokines
Cell signal molecules e.g. tumour necrosis factor/ interferons (trigger inflam & respond to infection)

Question 23

What stops production of blood forming cells which is lethal without treatment?

Answer 23

X-irradiation

Question 24

What is G0 & how is it entered?

Answer 24

Resting phase entered from G1 if there is no mitogenic signal

Question 25

What is an aneuploid gamete?

Answer 25

Gametes that receive an incorrect no of chromosomes

Question 26

Examples of cells in G0 phase

Answer 26

Post-mitotic cells e.g. neurones remain in G0 permanently

Haematopoietic & liver stem cells remain in G0 temporally until physiologically required

Question 27

What does p53 do?

Answer 27

Tumour suppressor protein that detects damaged DNA & initiated apoptosis

Question 28

Meiosis II resembles mitosis except that meiosis II:

Answer 28

1. Occurs without further DNA replication

2. The daughter cells have 1/2 the no of chromosomes of the parent

Question 29

What is nondisjucntion?

Answer 29

When chromosomes do not separate properly, daughter cells have extra chromosomes/ lack 1 or more
e.g. Down Syndrome - extra copy of chromosome 21
Disjunction = normal separation

Question 30

What do G1 & G1/S phase CDKs do?

Answer 30

Promote entry into the cell cycle

Question 31

How is the cell cycle exited?

Answer 31

1. Mitotic CDK activate APC/C (Anaphase-Promoting Complex) - initiate their own death
2. APC/c mediate degradation of mitotic cyclins
3. Inactivation of mitotic CDKs
4. Dephosphorylation of CDK substrates
5. Spindle disassembly/ chromosome decondensation/ nuclear envelope reformation

Question 32

What occurs in the event of DNA damage?

Answer 32

Damage activates transcription factor p53/ “tumour suppressor” that transcribes CDK inhibitor p21
p21 binds & inhibits cyclin-CDK complexes
So cells are arrested in G1 & G2
ATM & ATR phosphorylate p53 preventing its rapid degradation
In severe DNA damage p53 activates expression of genes that lead to apoptosis

Damage detected by protein kinases ATM & ATR
initiate recruitment of adapter proteins & protein kinases Chk1 & Chk2 that cause cell cycle arrest/ apoptosis

Question 33

Genetic basis of progeria

Answer 33

Mutation in LMNA gene that codes for lamina A of nuclear envelope

Question 34

How do progeria sufferers usually die?

Answer 34

Atherosclerosis leading to heart attack/ stroke

Question 35

Difference between apoptosis & necrosis?

Answer 35

Apoptosis - cells shrink, condense & fragment, DNA fragments & nuclei condense, intracellular constituents not released into extracellular milieu
Necrosis - cell death in response to tissue damage, cells swell & burst releasing intracellular contents

Question 36

Centrosomes

Answer 36

At poles of cell where spindles attack