cell division

Question 1

how are new cells made?

Answer 1

by duplicating ones that already exist

Question 2

what is the cell cycle?

Answer 2

where a cell reproduces by performing a sequence of events in which it duplicates its contents and then divides into two

Question 3

what are the two types of cell division?

Answer 3

vegetative division
reproductive division

Question 4

what is vegetative division?

Answer 4

each daughter cell is genetically identical to parent cell

Question 5

what is reproductive cell division?

Answer 5

number of chromosomes in daughter cells is reduced by half to produce haploid gametes

Question 6

what is the most important stage in the cell cycle?

Answer 6

DNA synthesis

Question 7

what are the three steps of cell replication?

Answer 7

cell growth and chromosome replication
chromosome segregation
cell division

Question 8

how is cell division stimulated/blocked in multicellular organisms?

Answer 8

control system is highly responsive to signals from other cells

Question 9

how many stages of cell cycle is there in eukaryotes?

Answer 9

four

Question 10

what is cytokinesis?

Answer 10

cell splits in two

Question 11

what are the four phases of the cell cycle?

Answer 11

G1
S
G2
M

Question 12

what happens in the S phase?

Answer 12

DNA replication

Question 13

what happens in the M phase?

Answer 13

mitosis
cytokinesis

Question 14

how long does the s phase take?

Answer 14

~ 11 hours in humans

Question 15

how long does the M phase take?

Answer 15

1 hour

Question 16

what is the purpose of the G1 and G2 phases?

Answer 16

allow more time for growth

Question 17

how long does it take to duplicate chromosomes in comparison to other stages of cell cycle?

Answer 17

much less time that to grow and double mass of proteins and organelles

Question 18

what does G phase stand for?

Answer 18

gap phase

Question 19

what is the interphase?

Answer 19

G1, S and G2 together

Question 20

when are decisions made in the cell cycle?

Answer 20

at checkpoints that decide whether the cell can proceed into each stage

Question 21

what are terminally differentiated cells?

Answer 21

cells that can withdraw permanently from the cell cycle, permanently stopping cell division

Question 22

what are example of terminally differentiated cells?

Answer 22

nerve or muscle cells

Question 23

what are cyclins?

Answer 23

a class of protein that control the cell cycle

Question 24

what do cyclins do?

Answer 24

activate kinases

Question 25

what are kinases?

Answer 25

enzymes that attach phosphate groups by phosphorylation

Question 26

what do CDKs stand for?

Answer 26

cyclin dependent kinases

Question 27

what is the most common way by which cells switch the activity of a protein on or off?

Answer 27

phosphorylation or dephosphorylation

Question 28

what does protein phosphorylation do?

Answer 28

regulate protein activity

Question 29

how are proteins modified in eukaryotes?

Answer 29

covalent addition of one or more phosphate groups

Question 30

what do protein kinases catalyse?

Answer 30

transfer of a phosphate group from ATP to an amino acid side chain of the target protein

Question 31

what is the removal of a phosphate group catalysed by?

Answer 31

protein phosphatase

Question 32

what is protein phosphatase?

Answer 32

an enzyme

Question 33

can phosphorylation increase or decrease protein's activity?

Answer 33

either

Question 34

what does DNA damage do?

Answer 34

blocks cell division

Question 35

how can DNA damage take place?

Answer 35

spontaneous chemical reactions errors in DNA replication exposure to radiation or certain chemicals

Question 36

what is an important mediator protein?

Answer 36

p53

Question 37

what happens when DNA is damaged?

Answer 37

protein kinases are recruited to the site of damage and initiate a signalling pathways that results in phosphorylation of p53

Question 38

what does phosphorylation of p53 do?

Answer 38

prevents it being targeted for destruction by the cell so is then free to bind to a gene and stimulate its transcription protein encoded by that gene binds to and inactivates a cyclin which results in the arrest of of the cell in G1

Question 39

what are the two forms of cell division and replication?

Answer 39

mitosis and meiosis

Question 40

how does meiosis and mitosis compare?

Answer 40

meiosis is an extended form of mitosis, involving one round of DNA replication followed by two round of cell division

Question 41

what are cells of most eukaryotic organisms?

Answer 41

diploid

Question 42

what does diploid mean?

Answer 42

the cells contain two slightly different copies of each chromosome, one from each parent

Question 43

what type of cells does meiosis produce? what about mitosis?

Answer 43

meiosis makes 4 haploid gametes per cell mitosis makes 2 diploid daughter cells per cell

Question 44

how many copies of each chromosome does haploid cells have after meiosis?

Answer 44

one of each

Question 45

what happens to haploid cells in many organisms after meiosis?

Answer 45

differentiate into gametes

Question 46

what are gametes?

Answer 46

specialised cells (egg and sperm)

Question 47

when does the reproductive cycle end in haploid organisms?

Answer 47

when a sperm and egg fuse to form a diploid zygote with the potential to form a new individual

Question 48

what are the difference between the gametes produced by males and females in haploid organisms?

Answer 48

females produce large and non motile eggs males produce small and motile sperm

Question 49

what is meiosis?

Answer 49

a special form of nuclear division involved in sexual reproduction

Question 50

why else do haploid organisms undergo meiosis and what happens in this process?

Answer 50

for cell division they remain haploid

Question 51

what happens in sexual reproduction of diploid organisms?

Answer 51

two cells undergo meiosis to form gametes fertilisation diploid zygote formed mitosis takes place diploid organisms formed

Question 52

what happens in sexual reproduction of haploid organisms?

Answer 52

2 haploid cells mate to form a diploid zygote meiosis to form 4 haploid cells mitosis to form 8 haploid cells

Question 53

how are organ and body size determined?

Answer 53

by cell growth, division and death

Question 54

how are cell growth, division and death regulated?

Answer 54

by intracellular programmes and extracellular signal molecules

Question 55

what are the classes of signalling molecule?

Answer 55

mitogens growth factors survival factors

Question 56

what do mitogens do?

Answer 56

stimulate cell division via cyclins

Question 57

what do growth factors do?

Answer 57

stimulate cell growth by increasing cell mass by promoting biosynthesis

Question 58

what do survival factors do?

Answer 58

promote cell survival by suppressing apoptosis

Question 59

what is apoptosis?

Answer 59

programmed cell death

Question 60

when do normal cells stop growing?

Answer 60

once they have formed a confluent monolayer

Question 61

how is density dependent inhibition on cell division assessed?

Answer 61

using a wound healing assay: cells are mechanically disrupted and then the rate of recovery can be measured

Question 62

what happens in prokaryotic cell division?

Answer 62

binary fission

Question 63

what type of cell division is binary fission?

Answer 63

vegetative

Question 64

what happens to the genetic material in binary fission

Answer 64

segregated equally into two identical daughter cells

Question 65

how many cells does each cell divide into in binary fission, mitosis and meiosis?

Answer 65

each cell divides into 2

Question 66

what are germ cells?

Answer 66

gametes

Question 67

when is an important checkpoint?

Answer 67

at S phase (DNA synthesis stage)