Cell division, Mitosis and Meiosis

Question 1

what happens when a cell is too big or too small

Answer 1

too small- cant contain organelles and molecules

too big- not adequate for exchange of materials

Question 2

how long is the duration of the cell cycle in

a) Yeast
b) human
c) e. coli

Answer 2

a) 24 hours
b) 90 minutes
c) 60 minutes

Question 3

what cells only divide occasionally

Answer 3

skin fibroblasts and liver cells

Question 4

what are the three stages of the cell cycle

Answer 4

• Interphase
• Mitosis
• Cytokinesis

Question 5

what parts is interphase composed of

Answer 5

• G1 (Gap1)
• S (Synthesis)
• G2 (Gap2)

Question 6

what is the longest phase in the cell cycle

Answer 6

interphase

Question 7

what happens during G1

Answer 7

• Cell doubles in size
• Cell produces all of the structures it needs to carry out its functions,
metabolically active
(cell living its normal life)

Question 8

what happens during S phase

Answer 8

cell makes a copy of its DNA (to get directions for its function and survival)

Question 9

what happens during G2 phase

Answer 9

• Cell prepares to divide
• Cell produces structures needed for cell division
(preparation checking phase)

Question 10

what two processes are involved in M phase

Answer 10

Mitosis and cytokinesis

Question 11

what happens during prophase of mitosis

Answer 11

1. Chromosomes become visible (chromatids condense)
2. Centrioles move to opposite poles
3. spindle fibers grow from centrioles and radiate to centre
4. Envelope breaks down and nucleolus disappears

Question 12

what happens during Metaphase

Answer 12

• chromosomes thicken more
• line up at centre
• fibers attach

Question 13

what happens during anaphase

Answer 13

spindle fibers pull sister chromatids apart, spindle fibers shorten, moving to opposite ends

Question 14

what happens during telophase

Answer 14

• nuclear membrane forms around each end
• nucleolus reforms
• chromosomes become chromatids (less thick)

Question 15

what can identify a cell in S phase

Answer 15

radioactive thymidine (3H Thymidine)

Question 16

what else can be used to determine cellular

Answer 16

incubation of cells with a fluorescent dye that bind to DNA using flow cytometer

Question 17

what occurs during cytokinesis

Answer 17

division of the cytoplasm

Question 18

when does the start regulatory point occur in yeast

Answer 18

late in G1. it controls progression from G1 to S phase

Question 19

what is the regulatory point in animals

Answer 19

restriction point (in late G1)

Question 20

when does the cell enter the G0 stage

Answer 20

if growth factors are not available during G1. Cells are still metabolically active but have stopped growth and reduced rate of protein synthesis

Question 21

until when are skin fibroblasts arrested in G0

Answer 21

until they are stimulated to divide as required to repair damage from a wound

Question 22

what triggers proliferation of skin fibroblasts

Answer 22

platelet-derived growth factor

Question 23

what are the functions of S phase checkpoint

Answer 23

1. monitoring of integrity of DNA

2. quality control monitor to promote repair of errors during replication

Question 24

what is the function of the G2 checkpoint

Answer 24

1. prevents the initiation of mitosis until DNA replication is completed.
2. prevents initiation of M before completion of S

Question 25

what is the function of M phase checkpoint

Answer 25

monitor alignment of chromosomes on mitotic spindle

Question 26

what are cyclins

Answer 26

most important core cell cycle regulatory proteins

Question 27

what are the four basic types of cyclins found in most eukaryotes

Answer 27

G1 cyclins, G1/S cyclins, S cyclins, and M cyclins

Question 28

what are CDKs

Answer 28

they are kinases (enzymes that phosphorylate specific target proteins)

Question 29

what happens when a cyclin attaches to CDK

Answer 29

1. activates CDK as a kinase

2. directs CDK to a specific set of proteins

Question 30

what is Rb

Answer 30

a tumor suppressor gene whose inactivation leads to tumor development

Question 31

describe what happens at the G1 checkpoint

Answer 31

if cyclin is absent, the tumor suppressor attaches to the gene group and represses transcription. if cyclin is present then the tumor suppressor is phosphorylated and cannot attach to the gene group and transcription occurs

Question 32

what restricts DNA replication to once per cel cycle

Answer 32

MCM helicase proteins which binds to the ORC

Question 33

what activates kinase activity of ATM

Answer 33

DNA damage caused by ionising radiation (double-strand DNA breaks)

Question 34

what activates ATR kinase activity

Answer 34

in response to a different set of DNA lesions, including those caused by UV light

Question 35

what does the Cdk1/cyclinB complex (MPF–maturation promoting factor) activate

Answer 35

• condensins,
• components of the nuclear envelop,
• Golgi matrix proteins and
• proteins associated with centrosomes and microtubules.

Question 36

what is the function of the cortical granules

Answer 36

Makes the zona pellucida impenetrable to sperm (after fertilisation) to prevent polyspermy

Question 37

what is the germinal epithelium

Answer 37

outer layer of cells in the ovary

Question 38

what is the function of the primary follicles

Answer 38

contains the primary oocyte surrounded by a single layer of supporting follicle cells

Question 39

what is the function of the mature follicle

Answer 39

contains the secondary oocyte, ready for ovulation

Question 40

what is the medulla

Answer 40

central main body of the ovary (blood vessels, lymph and nerves)

Question 41

once activated, what do ATM and ATR phosphorylate and activate

Answer 41

CHK1 and CHK2 kinases which then phosphorylate an inhibit the Cdc25A and Cdc25C protein phosphatases

Question 42

what is the function of Cdc25A and Cdc25C

Answer 42

required to activate Cdk2 and Cdk1

Question 43

what does inhibition of Cdc25A and Cdc25C cause

Answer 43

leads to arrest at the DNA damage checkpoints in G1, S and G2