3.2.2 All Cells Arise From Other Cells

Question 1

what are the 3 main stages of the cell cycle?

Answer 1

interphase
mitosis
cytokinesis

Question 2

what are the 3 phases within interphase?

Answer 2

G1 Phase
S Phase
G2 Phase

Question 3

what happens within the G1 Phase of the cell cycle?

Answer 3

cell grows as organelles are replicated and proteins are synthesised - enzymes needed for DNA replication - the cell prepares for replication

Question 4

what happens within the S (synthesis) phase in the cell cycle?

Answer 4

DNA replicates (semi-conservative replication) resulting in chromosomes made up of 2 identical sister chromatids

Question 5

what happens within the G2 Phase of the cell cycle?

Answer 5

cell continues to grow as production of spindle proteins and other components needed for mitosis takes place

Question 6

when do the centrioles mature and migrate to either pole of the cell?

Answer 6

at the end of G2 in preparation for mitosis

Question 7

what happens during mitosis (overview)?

Answer 7

parent cell divides to produce 2 genetically identical daughter cells

Question 8

why does mitosis occur?

Answer 8

it is needed for the growth of multicellular organisms and repairing damaged tissues

Question 9

what are the 4 phases within mitosis?

Answer 9

Prophase
Metaphase
Anaphase
Telophase

Question 10

what happens during prophase?

Answer 10

chromatin shortens and thickens to form visible chromosome structures
the nucleur envelope disappears

Question 11

what happens during metaphase?

Answer 11

chromosome (2 chromatids) structures line up along the equator of the cell. centrioles produce protein fibres called spindle fibres which extend and attach to the centromere

Question 12

what happens during anaphase?

Answer 12

centromere splits as spindle fibres contract pulling one of each genetically identical sister chromatids to either pole

Question 13

what happens during telophase?

Answer 13

chromatid unwinds (becomes long and thin), the nucleur envelope reforms around chromatin at either pole, cell membrane folds inwards at equator.

Question 14

how does the cell wall begin to form during mitosis in a plant cell?

Answer 14

cell plates begin on the equator

Question 15

what happens during cytokinesis?

Answer 15

the cytoplasm divides into 2, each containing a nuclei produced in mitosis, there are now 2 genetically identical daughter cells

Question 16

how do you calculate mitotic index

Answer 16

No of cells undergoing mitosis/total No of cells visible

Question 17

what form is mitotic index given in?

Answer 17

decimal form

Question 18

what can high mitotic index be a sign of?

Answer 18

high mitotic index means that the cell cycle/mitosis is happening quickly which could be a sign of cancerous cells

Question 19

what can uncontrolled cell division lead to?

Answer 19

the formation of tumours and cancers

Question 20

what do cancer treatments do?

Answer 20

they are directed at controlling the rate of cell division

Question 21

define how cancer occurs

Answer 21

due to uncontrolled cell division, and occurs when the rate of cell multiplication is faster than the rate of cell death

Question 22

what causes cancer?

Answer 22

mutations to the genes involved in the regulation of mitosis and the cell cycle

Question 23

what is a side effects of the cancer drugs?

Answer 23

cancer drugs can disrupt the cell cycle of normal ‘healthy’ cells

Question 24

why is the side effect of a cancer drug not a serious concern?

Answer 24

cancer cells divide more rapidly than normal ‘healthy’ cells, since the drugs work more effectively against rapidly dividing cells the cancer cells are more susceptible
however some rapidly growing ‘healthy’ cells can be targeted e.g. hair cells

Question 25

describe the structure of a chromosome?

Answer 25

2 strands, each called a chromatid joined in the middle by a centromere - chromatids are genetically identical

Question 26

what are DNA molecules wound around?

Answer 26

proteins called histones

Question 27

give an overview of binary fission?

Answer 27

the replication of circular DNA and plasmids, and the the division of the cytoplasm to produce 2 daughter cells each with a single copy of the circular DNA and a variable number of copies of plasmids

Question 28

what is the first step of binary fission

Answer 28

circular DNA and plasmid(s) replicate (main DNA loops is replicated once but plasmids can be replicated many times)

Question 29

what is the second and third step of binary fission?

Answer 29

cell grows in size and DNA loops move to opposite poles of the cell cytoplasm begins to divide and new cell wall begins to form

Question 30

what is the final step of binary fission?

Answer 30

cytoplasm divides into 2 daughter cells are produced. each daughter cell has 1 copy of the circular DNA but can have a variable number of sops of plasmid(s)

Question 31

why can't viruses undergo cell division?

Answer 31

they are non-living

Question 32

how do viruses replicate?

Answer 32

through viral replication

Question 33

give an overview of viral replication

Answer 33

the inject their DNA or RNA into the host cell, the host cell then replicates the genetic material and proteins from the virus using the host cells enzymes and ribosomes