CELLS 2 (specialisation, mitosis, cell cycle & cancer)

Question 1

what are the two genes called that control cell division?

Answer 1

tumour supressor gene and proto-oncogenes

Question 2

what does the tumour suppressor gene do in cell division?

Answer 2

reduce division by promoting apoptosis

Question 3

what does the proto-oncogenes do in cell division?

Answer 3

increase cell division by promoting the cell cycle

Question 4

what is apoptosis in terms of the tumour suppressor gene?

Answer 4

when cells self destruct in order to reduce rate of division

Question 5

what is the role of the 2 genes that control the cell cycle?

Answer 5

• cells divide at a constant rate
• dead or worn out cells are replicated

Question 6

what happens if the tumour suppressor or porto-oncogene is mutated?

Answer 6

tumours can form

Question 7

what are the two types of tumours?

Answer 7

Benign (non cancerous) & malignant (cancerous)

Question 8

cause of cancer

Answer 8

damaged or mutated tumour suppressor or proto-oncogene leading to uncontrolled cellular division = tumours

Question 9

What is the difference between a malignant and benign tumour?

Answer 9

M : cancerous & form secondary tumours via the blood system in metastasis

B: non-cancerous & don’t invade neighbouring tissues ( no metastasis )

Question 10

what’s one way that a benign tumour can be harmful?

Answer 10

They can cause blockages which can increase the pressures on certain organs

Question 11

how does chemotherapy work?

Answer 11

• prevents the DNA from cancer cells from replicating
• inhibits metaphase (chromosomes lining up) by interfering with spindle formation

Question 12

What are the three stages called during interphase?

Answer 12

Growth 1, Synthesis and Growth 2

Question 13

what happens during G1 phase in interphase?

Answer 13

• cell grows
• proteins are made by the cell eg RNA + protein

Question 14

what happens during Synthesis (S) phase in interphase?

Answer 14

the DNA replicates so each chromosome has an identical sister chromatid

Question 15

what is a chromatid?

Answer 15

half of a chromosome (eg one arm)
-individual strand of dna

Question 16

define chromosome

Answer 16

long DNA molecule, made of nucleic acids in form of 2 identical sister chromatids

Question 17

what happens during G2 phase in interphase?

Answer 17

• cell grows bigger
• newly synthesised DNA is checked for error
• DNA is repaired
• biosynthesis ( organelles replicated )

Question 18

what is the order of the 4 stages in mitosis?

Answer 18

P-M-A-T
prophase, metaphase, anaphase, telephase

Question 19

what happens in cytokinesis?

Answer 19

the cell membrane and cytoplasm divide to form 2 identical daughter cells

Question 20

what happens during prophase?

Answer 20

• chromosomes are free in cytoplasm
• nucleolus breaks down and disappears
• spindle fibres begin to form from centrioles

Question 21

what is the nucleolus? & when is it broken down

Answer 21

section in nucleus (very centre) that produces ribosomes
- broken down during prophase

Question 22

what happens during metaphase?

Answer 22

• the chromosomes align along the equator
• spindle fibres formed by microtubules from the centrioles.

Question 23

what are the spindle fibres made of in a cell?

Answer 23

made of microtubules

Question 24

what happens during anaphase?

Answer 24

• centrometres divide
• individual chromatids pulled apart to opposing poles

Question 25

what is a centrometre

Answer 25

what holds the two sister chromatids together in a chromosome.

Question 26

what happens during telophase

Answer 26

• the nuclear envelope reforms
• the spindle disintegrates
• chromosome longer and thinner

Question 27

how do prokaryotic cells divide?

Answer 27

binary fission

Question 28

describe 4 stages in binary fission

Answer 28

1. plasmid & nucleoid (circular dna) replicated
2. cell grows
3. dna opposite poles
4. cytokinesis and formation of new cell wall made of peptidoglycan
   = 2 daughters cells

Question 29

what are 2 things that might happen to a cell when it becomes specialised?

Answer 29

Change shape + contents (eg. amount of organelles)

Question 30

define differentiation

Answer 30

when a cell becomes specialised for a particular function.

Question 31

which eukaryotic organelle in breaks down and hydrolyses foreign matter

Answer 31

lysosomes

Question 32

mitotic index calculation formula

Answer 32

number of cells with condensed chromosomes ( dividing) / total no. cells x 100

Question 33

how can you tell if a cell is dividing under a microscope

Answer 33

if the chromosomes are visible

Question 34

what’s is a mitotic cell?

Answer 34

a cell that replicates to replace damaged cells

Question 35

why take a cell sample from a root or shoot tip?

Answer 35

Cells are actively growing so the cells will be undergoing mitosis .

Question 36

benefits of binary fission

Answer 36

more efficient, less energy needed

Question 37

negatives of binary fission

Answer 37

mutations are inherited, reduced variation, all die in unfavourable conditions