mitosis

Question 1

cell cycle

Answer 1

the regulated sequence of events that occurs between cell divisions

Question 2

3 phases of the cell cycle:

Answer 2

interphase
nuclear division (mitosis)
cell division (cytokinesis)

Question 3

what happens during interphase?

Answer 3

the cell increases in mass and size and carries out its normal cellular functions

Question 4

3 phases of interphase:

Answer 4

G1 phase
S phase
G2 phase

Question 5

what happens in the G1 phase?

Answer 5

cells make the proteins required for growth (eg: enzymes)

Question 6

what happens in the S phase?

Answer 6

the DNA in the nucleus replicates

Question 7

what happens in the G2 phase?

Answer 7

the cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired

Question 8

what is mitosis?

Answer 8

nuclear division where two genetically identical haploid daughter cells are produced

Question 9

why is mitosis useful?

Answer 9

-it lets unicellular zygotes grow into multicellular organisms
-damaged tissues can be repaired by mitosis

Question 10

asexual reproduction

Answer 10

offspring are genetically identical to the single parent used to produce them

Question 11

prophase

Answer 11

-chromosomes condense and are visible
-the two centrosomes move towards opposite poles
-spindle fibres begin to emerge from the centrosomes
-the nuclear envelope breaks down

Question 12

metaphase

Answer 12

-centrosomes reach opposite poles
-chromosomes line up at the equator
-spindle fibres reach the chromosomes and attach to the centromeres

Question 13

anaphase

Answer 13

-the sister chromatids separate at the centromere
-spindle fibres begin to shorten
-the chromosomes are pulled to opposite poles by the spindle fibres

Question 14

telophase

Answer 14

-chromosomes arrive at opposite poles and begin to decondense
-nuclear envelopes reforms around each set of chromosomes
-the spindle fibres break down

Question 15

cytokines

Answer 15

the cytoplasm divides, this results in two genetically identical cells

Question 16

how do cancers start?

Answer 16

when changes happen in the genes that control cell division (mutation)

Question 17

how is mitosis affected in cancer?

Answer 17

uncontrolled mitosis, which forms a tumour

Question 18

what is an oncogene?

Answer 18

a mutated gene that causes cancer

Question 19

are mutations common?

Answer 19

yes

Question 20

do mutations usually have a negative effect?

Answer 20

no:
-most mutations either result in early cell death or result in the cell being destroyed by the body’s immune system

(most cells can be easily replaced, so these events usually have no harmful effect on the body)

Question 21

what are carcinogens?

Answer 21

any agents that may cause cancer

Question 22

examples of carcinogens:

Answer 22

-UV light
-tar in tobacco smoke
-X-rays

Question 23

which tumours don’t spread from their original site?

Answer 23

benign (don’t cause cancer)

Question 24

which tumours invade neighbouring tissue?

Answer 24

malignant (cause cancer)

Question 25

what do malignant tumours do to organs/tissue?

Answer 25

interfere with the normal functioning of the organ/tissue in which they have started to grow

Question 26

metastasis

Answer 26

cancer cells can break off the tumour and travel through the blood to form secondary growths in other parts of the body

Question 27

why is metastasis dangerous?

Answer 27

it can be very difficult to detect, locate and remove secondary tumours

Question 28

stages in the development of cancer

Answer 28

1) oncogenes arise due to carcinogens

2) cancerous cell does not respond to signals from other cells & continues to divide

3) cancerous cells aren’t removed by the immune system

4) the tumour gets bigger due to absorption of nutrients leading to rapid mitosis

5) tumour is supplied with blood, if the tumour is malignant, tumour cells spread in blood to other parts of the body

6) metastasis (tumour cells invade other tissues, secondary tumours form throughout the body)

Question 29

what mutated gene do most people with cancer posses?

Answer 29

a mutated p53 gene (a gene that helps to control cell growth)

Question 30

can viruses cause cancer?

Answer 30

yes, some oncoviruses cause cancers

Question 31

how do most current cancer treatments work?

Answer 31

by controlling the rate of mitosis