Topic 1.6: Cell Division

Question 1

Cell Cycle

Answer 1

The cell cycle is an ordered set of events that culminates in cell division

Question 2

Main Phases of the Cell Cycle

Answer 2

a) Interphase

b) M phase

Question 3

Interphase

Answer 3

An active phase of the cell cycle where many metabolic reactions occur

a) G1
b) S
c) G2

Question 4

G1

Answer 4

Cell grows and prepares for DNA replication

Question 5

S

Answer 5

Synthesis stage in which DNA is replicated

Question 6

G2

Answer 6

Cell finishes growing and prepares for cell division

Question 7

M Phase

Answer 7

The period of a cell cycle in which the cell and contents divide

a) Mitosis
b) Cytokinesis

Question 8

Mitosis

Answer 8

Nuclear division, whereby DNA is separated into two identical nuclei

Question 9

Cytokinesis

Answer 9

Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two

Question 10

Key events in Interphase for division (Doctor)

Answer 10

a) DNA replication (S)
b) Organelle duplication (G2)
c) Cell growth
d) Transcription / Translation
e) Obtain nutrients
f) Respiration

Question 11

How and when do chromosomes condense?

Answer 11

By supercoiling during mitosis

Question 12

Chromatin

Answer 12

a) DNA loosely packed

b) Accessible to transcription and translation

Question 13

Chromosome

Answer 13

a) DNA tightly packed
b) Inaccessible to transcription
c) Organized into chromosomes

Question 14

Sister chromatids

Answer 14

Genetically identical strands of DNA joined at a centromere

Question 15

Phases of Mitosis

Answer 15

a) Prophase
b) Metaphase
c) Anaphase
d) Telophase

Question 16

Prophase

Answer 16

a) DNA supercoils and condenses (forms visible chromosomes)
b) Nuclear membrane dissolves
c) Centrosomes move to poles and begin to produce spindle fibres

Question 17

Metaphase

Answer 17

a) Centrosome spindle fibres attach to the centromere of each chromosome
b) Spindle fibres contract and move the chromosomes towards the cell centre
c) Chromosomes form a line along the equator of the cell

Question 18

Anaphase

Answer 18

a) Spindle fibres continue to contract
b) Sister chromatids separate and move to opposite sides of the cell
c) Sister chromatids are now regarded as two separate chromosomes

Question 19

Telophase

Answer 19

a) Chromosomes decondense (DNA forms chromatin)
b) Nuclear membranes form around the two identical chromosome sets
c) Cytokinesis occurs concurrently

Question 20

Cytokinesis

Answer 20

a) Cytoplasmic division occurs to divide the cell into two daughter cells
b) Each daughter cell contains one copy of each identical sister chromatid
c) Daughter cells are genetically identical

Question 21

Interphase

Answer 21

a) DNA is uncondensed (chromatin)
b) DNA is replicated (S phase) to form genetically identical sister chromatids
c) Cell grows in size and organelles are duplicated (G1 and G2)

Question 22

Cytokinesis in Animals

Answer 22

Microtubules form a concentric ring and contract towards the centre (centripetal)

Question 23

Cytokinesis in Plants

Answer 23

Vesicles form at the cell centre and fuse outwards to form a cell plate (centrifugal)

Question 24

Mitotic index

Answer 24

Measure of the proliferation status of a cell population (i.e. number of dividing cells)

Question 25

Function of the Mitotic Index

Answer 25

a) The mitotic index will be elevated during growth and repair processes b) Acts as a prognostic tool for cancer

Question 26

Cyclins

Answer 26

Proteins that control the progression of the cell cycle

Question 27

Cyclins process

Answer 27

a) Cyclins bind to cyclin dependent kinases (CDKs) b) The activated complex phosphorylates proteins involved in specific cell cycle events (e.g. centrosome duplication) b) After the event has occurred, the cyclin is degraded and the cyclin dependent kinase is rendered inactive

Question 28

Cyclin Expression Patterns

Answer 28

a) Cyclin concentrations need to be tightly regulated to ensure the cell cycle progresses in a proper sequence b) Cyclin levels will peak when their target protein is required for function and remain at lower levels after

Question 29

Tumours

Answer 29

Abnormal cell growths resulting

Question 30

Cancer

Answer 30

Diseases caused by uncontrolled cell division

Question 31

Types of tumour cells

Answer 31

a) Benign (Remain in their original location) | b) Malignant (Invade neighbouring tissue)

Question 32

Metastasis

Answer 32

Spread of cancer from an original site to a new body location (forming a secondary tumor)

Question 33

Mutagen

Answer 33

Agent that changes the genetic material of cells

Question 34

Examples of mutagens

Answer 34

a) Radiation (X-rays / UV) b) Reactive oxygen species and metals c) Viruses / Bacteria

Question 35

Carcinogens

Answer 35

Mutagens that lead to the formation of cancer

Question 36

Oncogene

Answer 36

Gene that has the potential to cause cancer

Question 37

Proto-oncogenes (Gas)

Answer 37

Stimulate cell growth and proliferation

Question 38

Tumour suppressor (Brakes)

Answer 38

Repress cell cycle progression

Question 39

Correlation between smoking and incidence of cancers

Answer 39

a) There is a strong positive correlation between the frequency of smoking and the incidence of cancer b) Cigarette smoke contains >60 known carcinogens

Question 40

Mechanisms of Cell Death

Answer 40

a) Necrosis (uncontrolled ‘cell homicide’) | b) Apoptosis (programmed ‘cell suicide’)

Question 41

Necrosis (uncontrolled ‘cell homicide’)

Answer 41

a) The cell loses functional control due to injury, toxins, etc. b) There is a destabilization of the membranes, leading to swelling c) The cell bursts and releases its contents (causing inflammation)

Question 42

Apoptosis (programmed ‘cell suicide’)

Answer 42

a) It is a controlled event triggered by mitochondrial proteins b) Cell contents are packaged in membranous protrusions c) The cell fragments into apoptotic bodies which are recycled

Question 43

Cell Cycle Checkpoints

Answer 43

a) G1 checkpoint b) G2 checkpoint c) Metaphase checkpoint

Question 44

G1 checkpoint

Answer 44

a) Monitors potential growth conditions (nutrients, etc.) | b) Assesses level of DNA damage (from UV, etc.)

Question 45

G2 checkpoint

Answer 45

a) Monitors state of pre-mitotic cell (suitable size, etc.) | b) Identifies and repairs any DNA replication errors

Question 46

Metaphase checkpoint

Answer 46

Ensures proper alignment (prevents aneuploidy)