ANAT: cell cycle

Question 1

What are the 4 stages of the mitotic cell cycle?

Answer 1

G1 phase, S phase, G2 phase, M phase

Question 1

Describe the G1 phase

Answer 1

Usually the longest stage, prepares the cell for replication and doubling in cell mass

Question 2

Describe the S phase

Answer 2

DNA replicated to produce 2 identical copies of each chromosome

Question 3

Describe the G2 phase

Answer 3

Preparation for mitosis

Question 4

Describe the M phase

Answer 4

Mitosis occurs

Question 5

List the 6/7 stages of mitosis

Answer 5

Interphase, early prophase, late prophase, metaphase, anaphase, telophase, cytokinesis

Question 6

Describe the pathway through which the G1/S transition is regulated

Answer 6

Cyclin D produced > Cyclin D binds to CDK 4 > Cyclin D-CDK 4 complex causes transcription and production of Cyclin E > cyclin E binds to CDK 2 > complex activated for S-phase

Question 7

Describe the processes through which S-phase is regulated

Answer 7

Cyclin-CDK complexes phosphorylate pre-replication complex proteins, however new PRCs are prevented from forming > genome replicated ONCE

Question 8

Describe the events that occur in interphase

Answer 8

G1 phase, S phase, G2 phase

Question 9

Describe the events that occur in early prophase

Answer 9

Cells are 4N, chromatin condenses to form chromosomes

Question 10

Describe the events that occur in late prophase

Answer 10

Nuclear envelope and nucleoli disappears, mitotic spindle apparatus forms in cytoplasm

Question 11

Describe the events that occur in metaphase

Answer 11

Spindle attaches to chromosomes at centromeres, chromosomes are most condensed, move to metaphase plate

Question 12

Describe the events that occur in anaphase

Answer 12

Centromeres divide, chromatids separate to form 2 identical chromosomes, spindle fibres shorten

Question 13

Describe the events that occur in telophase

Answer 13

Nuclear envelope and nucleoli start to reform, AFTER cytokinesis: cells cleaved, both cells re-enter interphase

Question 14

How does Rb function?

Answer 14

Negative regulator: active Rb prevents mitosis, must be inactivated via phosphorylation

Question 15

How does p53 function?

Answer 15

Negative regulator: active p53 promotes transcription of inhibitors of cyclin-CDK complexes

Question 16

Describe the events that occur in prophase I

Answer 16

Nuclear envelope breaks down, chromosomes condense, CROSSING OVER occurs

Question 17

Describe the events that occur in metaphase I

Answer 17

Homologues align on the metaphase plate

Question 18

Describe the events that occur in anaphase I

Answer 18

Spindle fibres shorten, homologues pulled to opposite cell poles

Question 19

Describe the events that occur in telophase I

Answer 19

Nuclear membrane reforms, cytokinesis

Question 20

Describe the events that occur in prophase II

Answer 20

Nuclear membrane disappears, spindle fibres form

Question 21

Describe the events that occur in metaphase II

Answer 21

Chromosomes align on the metaphase plate, which has been rotated 90 degrees

Question 22

Describe the events that occur in anaphase II

Answer 22

Sister chromatids pulled to opposite poles as spindle fibres shorten

Question 23

Describe the events that occur in telophase II

Answer 23

Disassembly of spindle fibres, nuclear envelope reforms, cytokinesis

Question 24

Describe Turner’s syndrome

Answer 24

X, typical webbed neck, cognitive ability unaffected

Question 25

Describe Kleinfelter’s syndrome

Answer 25

XXY, mild, carriers can be unaware of their condition

Question 26

PEDs

Answer 26

Trisomy 13, 18, 21

Question 27

Other names for apoptosis

Answer 27

Cell suicide, programmed cell death

Question 28

Triggers for apoptosis

Answer 28

Intracellular and extracellular signals

Question 29

List the 7 steps of apoptosis

Answer 29

1. Caspase action: proteinaceous cytoskeleton broken down
2. Cell shrinkage
3. Pyknosis: chromatin condenses into compact patches against nuclear envelope
4. Nuclear envelope breakdown
5. Karyorrhexis: nucleus/DNA destructive fragmentation
6. Blebbing: cell membrane buds off in irregular blebs
7. Phagocytosis: blebs form apoptotic bodies that are phagocytosed

Question 30

Triggers of necrosis

Answer 30

External factors, including frostbite, infection, injury

Question 31

Characteristics of necrosis

Answer 31

Cells swell and burst, release intracellular contents, damage surrounding cells, lack of chemical signalling > no phagocytosis