3.2.2 mitosis and cell cycle

Question 1

what is mitosis?

Answer 1

mitosis is the division of a cell that results in each of the daughter cells having an exact copy of the DNA of the parent cell.

preceded before interphase

Question 2

what are the four stages of mitosis?

Answer 2

1. P = Prophase
2. M = Metaphase
3. A = Anaphase
4. T = telophase

Question 3

describe prophase

Answer 3

chromosomes become visible, later shorten and thicken

centrioles move to opposite poles of the cell

spindle fibres form from each centriole
all spindle fibres = spindle apparatus

nucleolus disappears and the nuclear envelope breaks down

chromosomes are drawn to equator of cell by the spindle fibres attached to centromere

Question 4

describe metaphase

Answer 4

chromosomes are made up of two chromatids

each chromatid is an identical copy of DNA from the parent cell
joined by centromere

chromosomes are pulled along the spindle apparatus and arrange themselves along the equator of the cell

Question 5

describe anaphase

Answer 5

CENTROME DIVIDES
SPINDLE CONTRACTS
CHROMOTIDS TO OPPOSITE POLES

Question 6

describe telophase and cytokinesis

Answer 6

chromosomes reach poles and become longer and thinner
disappearing and leaving chromatin

spindle fibres disintegrate and nuclear envelope and nucleolus reform

Question 7

what is interphase?

Answer 7

not a resting stage, there is intense activity

divides into three phases: G1, S and G2

Question 8

what is the importance of mitosis?

Answer 8

growth = all cells must be genetically identical

repair = if all cells are damaged or die, all now cells must be produce to replace

asexual reproduction = divide by mitosis to reproduce identical offspring

Question 9

what are the two types of nuclear division?

Answer 9

mitosis = when each nucleus divides into two DAUGHTER CELLS, containing identification diploid sets of chromosomes

meiosis = nucleus divides into four DAUGHTER CELLS, each containing half the number of chromosomes, occurs in sexual reproduction

Question 10

treatment of cancer

Answer 10

chemotherapy
prevents dna replication and inhibits metaphase by interfering with spindle formation
more effective against rapid dividing cells, but normal cells which divide rapidly are vulnerable to damage

Question 11

what are malignant tumours?

Answer 11

cancerous tumours that spread from site of origin

grow rapidly, less compact and more life threatening

develop own blood and lymph supply which can transport malignant cells to other sites

they can move around the body

Question 12

benign tumours

Answer 12

tumour does not spread from site of origin
may not be harmful if tumour stays in place
grow slowly and relatively compact
less dangerous then malignant but can cause discomfort and reduce functioning of organs

Question 13

describecancer

Answer 13

isn’t one disease around 200 (all have similar features)
result of uncontrolled mitosis because of an acceleration gene
leads to an irregular mass of cells BENIGN OR MALIGNANT

Question 14

what are the 3 stages of cell cycle

Answer 14

1. interphase = which occupies most of the cell cycle
   also known as resting phase
2. mitosis = nucleus divides into two
3. cytokinesis = cytoplasm divides to produce two new cells

Question 15

where does viral replicationoccur?

Answer 15

INSIDE HOST CELL

viral nucleic acid enters the host cell machinery = eg ribosomes and synthesises all new viral components

Question 16

bacteriophage infecting a bacterium

Answer 16

viruses cannot do anything until they enter the cell because they are not living things
cannot be destroyed by antibiotics, inside living cells

Question 17

summary of bacterial replication

Answer 17

circular DNA molecule replicates and both copies attach to the cell membrane

plasmids replicate

cell membrane pinches in between the two DNA molecules, dividing the cytoplasm in two

new cell wall forms between the two molecules of DNA

Question 18

how does bacteria replicate?

Answer 18

BINARY FISSION

not mitosis, as there is no nucleus and no mitotic spindle

dna replication happens at the same time as DNA
no nuclear membrane to break down and rebuild

Question 19

what is the structure of viruses?

Answer 19

have a protein coat and genetic material (DNA AND RNA) and attachment proteins

Bacteria are prokaryotes