1.6 Cell Division

Question 1

Cell Cycle

Answer 1

ordered set of events which culminates in the division of a cell into two daughter cells

Question 2

Cell Cycle can be roughly divided into 2 main phases

Answer 2

Interphase and M phase

Question 3

Interphase

Answer 3

• btw 2 successive divisions

- G1 / S / G2

Question 4

Interphase: G1

Answer 4

first intermediate gap stage in which the cell grows and prepares for DNA replication

Question 5

Interphase: S

Answer 5

Synthesis stage in which DNA is replicated

Question 6

Interphase: G2

Answer 6

Second intermediate gap stage in which the cell finishes growing and prepares for cell division

Question 7

M phase

Answer 7

The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells

Question 8

M phase is comprised of 2 distinct stages:

Answer 8

Mitosis

Cytokinesis

Question 9

M phase: Mitosis

Answer 9

Nuclear division, whereby DNA ( as condensed chromosomes) is separated into two identical nuclei

Question 10

M phase: Cytokinesis

Answer 10

Cytoplasmatic Division, whereby cellular contents are segregated and the cell splits into two

Question 11

Many events need to occur in interphase to prepare the cell for successful division

Answer 11

D na replication
O rganelle duplication
C ell growth
T ranscription/ Translation
O btain nutrients
R espiration ( cellullar)

Question 12

Dna Replication

Answer 12

Dna is copied during the S phase of Interphase

Question 13

Organelle Duplication

Answer 13

organelles must be duplicated for twin daughter cells

Question 14

Cell Growth

Answer 14

Cytoplasmi volume must increase prior to division

Question 15

Transcription / Translation

Answer 15

Key proteins and enzymes must be synthesised

Question 16

Obtain Nutrients

Answer 16

Vital cellular materials must be present before division

Question 17

Respiration ( Cellular)

Answer 17

ATP production is needed to drive the division process

Question 18

Chromatin

Answer 18

• DNA is usually packed within the nucleus as unravelled chromatin
• In this unravelled form, the DNA is accesible to transcriptional machinery and so genetic information can be translated
• DNA is organised as chromatin in all non dividing cells and throughout the process of interphase

Question 19

Before Mitosis (Interphase)

Answer 19

• DNA is present as uncondensed chromatin
• DNA is contained within a clearly defined nucleus
• Centrosomes and other organelles have been duplicated
• Cell is enlarged in preparation for division

Question 20

Prophase

Answer 20

• DNA supercoils and chromosomes condense
• Chromosomes are comprised of genetically identical sister chromatids (joined at a centromere)
• Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres
• The nuclear membrane breaks down and the nucleus dissolves

Question 21

Metaphase

Answer 21

• Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome
• Microtubule depolymerisation causes spindle fibres to shorten in length and contract
• This causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate)

Question 22

Anaphase

Answer 22

• Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate
• Once the chromatids separate, they are each considered an individual chromosome in their own right
• The genetically identical chromosomes move to the opposite poles of the cell

Question 23

Telophase

Answer 23

• Once the two chromosome sets arrive at the poles, spindle fibres dissolve
• Chromosomes decondense (no longer visible under light microscope)
• Nuclear membranes reform around each chromosome set
• Cytokinesis occurs concurrently, splitting the cell into two

Question 24

Cytokinesis

Answer 24

the process of cytoplasmic division, whereby the cell splits into two identical daughter cells

Question 25

Cytokinesis, animal cells

Answer 25

Microtubule filaments form a concentric ring around the centre of the cell Filament contraction create a cleavage furrow, which pinches off to form 2 cells Because this separation occurs from the outside and moves towards the centre, it is described as centripetal

Question 26

Cytokinesis, plant cells

Answer 26

Carbohydrate-rich vesicles form in a row at the centre of the cell (equatorial plane) The vesicles fuse to form an end plate, which extends out to separate the cell in two. Because this separation originates in the centre and moves laterally, it is described as centrifugal

Question 27

Necrosis

Answer 27

- premature death of cell - destabilisation of the membrane that leads to swelling and eventual lysis Released contents may cause inflamation

Question 28

Apoptosis

Answer 28

- controlled destruction of a cell in response to molecular signals - membrane bulges and contents are repackaged for removal Released content is recycled by other cells

Question 29

Tumours

Answer 29

caused by uncontrolled cell division and can occur in any tissue/organ

Question 30

tumours may be classed as

Answer 30

Benign: remains in original location Malignant: spreads to other tissue

Question 31

Metastasis

Answer 31

is the spread of cancer from an original site to a new body location

Question 32

Tumors may be caused by many factors

Answer 32

Mutagents: agents that cause DNA mutations Oncogenes: active genes that cause cancer

Question 33

Carcinogens

Answer 33

chemicals and agents that cause cancer, mutagens (viruses)

Question 34

Cigarretes contains

Answer 34

more than 60 carcinogens

Question 35

Mutagens

Answer 35

Agent that changes the genetic material of an organism (acting on DNA or the replicative machinery). - Physical: Sources of radiation including X-rays, ultraviolet light and radioactive decay - Chemical: DNA interacting substances including reactive oxygen species and metals - Biological: Viruses, certain bacteria and mobile genetic elements

Question 36

Cyclins

Answer 36

regulatory proteins that control the progression of cell cycle