cell division

Question 1

3 important reasons for cell division

Answer 1

development + growth
tissue maintenance
tissue repair

Question 2

define labile cells
example

Answer 2

continuously dividing cells
epithelial cells lining the skin

Question 3

define terminally differential state

Answer 3

cells that will not undergo cell division anymore

Question 4

which phase is the terminally differential state?
example of cells in this phase

Answer 4

G0
adult neurons + skeletal muscle cells

Question 5

what phase are most liver cells in? what happens if the liver is damaged?

Answer 5

G0
cells can regenerate by cell division

Question 6

define G1 phase

Answer 6

cells monitoring internal condition + external signals to decide for cell differentiation/ timing of the next division

Question 7

how is DNA packed in the G1 phase?

Answer 7

in the form of chromatin

Question 8

define G0 phase

Answer 8

quiescent state where cells remain as non-dividing cells

Question 9

define S phase

Answer 9

DNA double strands unwind and each strand is replicated
new strands are coiled around histones and form chromatin again

Question 10

define leading strand

Answer 10

synthesised continuously in the 5’ to 3’ direction

Question 11

define lagging strand

Answer 11

synthesised in Okazaki fragments in the 3’ to 5’ direction

Question 12

define Okazaki fragments

Answer 12

short segments

Question 13

what is the role of DNA ligase?

Answer 13

join the Okazaki fragments

Question 14

what is the role of DNA polymerase?

Answer 14

elongate the new strand by incorporating free nucleotides

Question 15

what is the role of topoisomerase?

Answer 15

relaxes the helix by making single-stranded breaks

Question 16

define G2 phase

Answer 16

transition from S to M
(may not be clear when cells are dividing rapidly)

Question 17

define M phase

Answer 17

mitosis (nuclear division) then cytokinesis (cell division)

Question 18

define prophase
what happens?

Answer 18

chromosome condensation
elongated chromosomes condense into much more compact chromosomes
nuclear envelope breaks down

Question 19

what happens in prometaphase?

Answer 19

replicated chromosomes become attached to the microtubules of the mitotic spindle

Question 20

define metaphase
what happens?

Answer 20

chromosome alignment
chromosomes align at the equator of the mitotic spindle ready for segregation

Question 21

define anaphase
what happens?

Answer 21

separation of sister chromatids
chromosomes move to opposite poles of the spindle

Question 22

what happens in telophase?

Answer 22

chromosomes de-condense and nucleus reforms
it is continuous to cytokinesis

Question 23

define karyotype

Answer 23

an individual’s number and structure of the chromosomes

Question 24

define aneuploidy

Answer 24

abnormal chromosome number

Question 25

define genome

Answer 25

all of an organism’s genetic information

Question 26

define gene

Answer 26

a functional unit of DNA encoding a protein

Question 27

define chromosome

Answer 27

long DNA with binding proteins

Question 28

define chromatin

Answer 28

DNA entangled with histone proteins

Question 29

define chromatids

Answer 29

newly copied chromosomes still joined by the centromere

Question 30

define autosome

Answer 30

non-sex chromosomes

Question 31

define sex chromosomes

Answer 31

X and Y chromosomes

Question 32

what are the 3 checkpoints for regulation?

Answer 32

G2
metaphase
G1

Question 33

define G2 checkpoint?
what does it check?

Answer 33

enter M
all DNA is replicated and it’s a favourable environment

Question 34

define metaphase checkpoint
what does it check?

Answer 34

exit M
all chromosomes are attached to the spindle

Question 35

define G1 checkpoint
what does it check?

Answer 35

enter S
it’s a favourable environment

Question 36

4 types of anticancer drug

Answer 36

block DNA synthesis
block mitotic spindle formation/ contraction
block Cyclin-Dependent Kinases (CDKs) that normally promote checkpoints
block specific signal transduction pathways

Question 37

define necrosis

Answer 37

cell death in response to acute insult
cells burst + contents spill over neighbouring cells and induce an immune response

Question 38

is necrosis pathological or physiological?

Answer 38

pathological

Question 39

define apoptosis

Answer 39

programmed cell death
cells shrink + condense, chromatin breaks up into fragments, cell surface changes such that macrophage can detect it + engulf it

Question 40

is apoptosis pathological or physiological?

Answer 40

physiological

Question 41

autophagy may prevent … …

Answer 41

cell death