2.2 All cells arise from other cells

Question 1

what are the 5 stages of mitosis

Answer 1

1. interphase
2. prophase
3. metaphase
4. anaphase
5. telophase

Question 2

describe interphase

Answer 2

cell grows
DNA and organelle are replicated

Question 3

describe prophase

Answer 3

chromosomes become shorter and thicker
centrioles divide and move to poles of the cells
spindle fibres form from these centrioles which are celled the spindle apparatus
nuclear membranes disintegrate and the nucleolus disappears

Question 4

describe metaphase

Answer 4

chromosomes visible as pair of chromatids joined at the centromere arrange themselves at the equator
they attach to the spindle fibres at the centromere

Question 5

describe anaphase

Answer 5

a very rapid phase
centromere divides and spindle fibres contract and shorten and pull separated chromosomes to opposite poles
the energy required for this is provided by mitochondria around the spindle fibres.

Question 6

describe telophase

Answer 6

chromosomes have reached the poles which uncoil and lengthen and become chromatin
nucleoli reappear and nuclear membrane reforms

Question 7

give the equation for mitotic index

Answer 7

number of actively dividing cells / total number of cells

Question 8

what are the 4 stages of division in eukaryotic cells

Answer 8

G1, S, G2 and M

Question 9

define cytokinesis

Answer 9

in animal cells is occurs by the cleavage of the cell membrane, the cytoplasm hen divides forming 2 daughter cells

Question 10

how to find the duration of a stage in mitosis

Answer 10

duration of any stage = number of cells in that stage / total number of cells x the cell cycle duration for that organism

Question 11

define cancer

Answer 11

uncontrolled growth of cells eating to tumors

Question 12

what are the 2 differences between benign and malignant

Answer 12

benign are slow growing and do not spread
malignant are fast growing and they spread beyond their original organ

Question 13

what are the 4 stages of growth of cancer

Answer 13

1. mutation in a gene that regulates the cell cycle, chances of mutation are increased by exposure to UV or harmful chemicals as it affects DNA bases
2. cell cycle is no longer controlled and apoptosis is no longer initiated
3. cells grow uncontrollably
4. tumour formation

Question 14

what is apoptosis

Answer 14

programmed cell death

Question 15

why does apoptosis occur

Answer 15

removing damaged cells from the body
menstrual cycle
forming new neural connections

Question 16

define metastasis

Answer 16

cells from a tumour breaking off, getting into blood stream and spreading to other parts of the body, this could result in secondary cancers

Question 17

name 2 types of cancer treatment

Answer 17

chemotherapy - using drugs
radiotherapy - using ionising radiation

Question 18

what is the main principle in chemotherapy

Answer 18

the need to block part of the cell cycle and prevent DNA replication

Question 19

how does chemotherapy work

Answer 19

adriamycin and cytotaxin stop DNA unwinding so it cannot replicate
it works by inhibiting spindle formation and vinca alkaloids prevent the spindle fibres forming to metaphase and anaphase cannot happen

Question 20

what cells are cancer drugs most effective on

Answer 20

rapidly dividing drugs