Cell division

Question 1

roles of mitosis

Answer 1

• tissue growth
• tissue repair
• asexual reproduction

Question 2

roles of meiosis

Answer 2

production of haploid gametes with genetic variation:
- crossing over
- independent assortment
- random fertilisation

Question 3

what occurs during G1?

Answer 3

• organelles replicate
• protein synthesis
• respiration
• cell increases in size (cytoplasm increases in volume)

Question 4

what occurs during the synthesis stage of the cell cycle?

Answer 4

• DNA replicated in the nucleus

Question 5

what occurs in G2?

Answer 5

• cell continues to increase in size
• spindle fibres form
• proteins for mitosis produced
• increase energy stores
• duplicated DNA checked for errors and corrected

Question 6

reasons for G0

Answer 6

• differentiation
• damaged DNA (not viable)
• cells become senescent (old/only go through the cell cycle a limited number of times)

Question 7

give an example of a type of cell that can reenter the cell cycle after G0

Answer 7

lymphocytes (B memory cells)

Question 8

name three cell cycle checkpoints and their position

Answer 8

• G1 checkpoint (after G1, before S or G0)
• G2 checkpoint (after G2, before mitosis)
• spindle assembly checkpoint/metaphase checkpoint (during metaphase)

Question 9

G1 checkpoint roles

Answer 9

• cell size
• nutrients
• growth factors
• DNA damage

Question 10

G2 checkpoint roles

Answer 10

• cell size
• DNA replication
• DNA damage

Question 11

spindle assembly checkpoint roles

Answer 11

• chromosome attachment and alignment to spindle fibres

Question 12

why can’t cells keep growing indefinitely?

Answer 12

as size increases, SA:V decreases and gas exchange, transport of nutrients etc would be inefficient

Question 13

blastocyst structure

Answer 13

• outer ball of totipotent cells (umbilical chord and placenta)
• pluripotent embryonic cells inside

Question 14

three potencies

Answer 14

• totipotent
• pluripotent
• multipotent

Question 15

totipotent

Answer 15

stem cells that can differentiate into any type of cell including placenta and umbilical chord cells

Question 16

pluripotent

Answer 16

stem cells that can form all body cells (excluding cells to make an umbilical chord or placenta)

Question 17

multipotent

Answer 17

stem cells that can only form a range of cells within a certain type of tissue

Question 18

example of multipotent animal cells

Answer 18

haemopoetic stem cells in bone marrow can differentiate into any blood cell

Question 19

what are iPSC?

Answer 19

induced pluripotent stem cells - adult stem cells which have been genetically modified to behave like embryonic stem cells

Question 20

why are embryos a better source than umbilical chords and bone marrow for stem cells?

Answer 20

• embryomic cells are pluripotent whereas the other two are only multipotent
• adult stem cells (umbilical and bone marrow) are likely to have accumulated more mutations

Question 21

prophase

Answer 21

• nuclear envelope breaks down
• chromatin fibres condense
• spindle fibres (microtubules) form from centrioles
• spindle fibres attach to centromeres of chromosomes

Question 22

metaphase

Answer 22

• chromosomes align on the metaphase plate/equator

Question 23

anaphase

Answer 23

• spindle fibres contract
• centromeres split and sister chromatids pulled to opposite poles

Question 24

telophase

Answer 24

• nuclear envelope forms around chromosomes
• chromatids/chromosomes uncoil to form chromatin

Question 25

cytokinesis in animal cells

Answer 25

microfilament ring (cytoskeleton) pulls plasma membrane inwards to create a cleavage furrow

Question 26

cytokinesis in plant cells

Answer 26

- golgi apparatus produces vesicles - vesicles assemble in the centre of the cell - vesicles fuse to split the cell - cell wall forms along new sections of membrane formed by vesicles

Question 27

prophase 1

Answer 27

- nuclear envelope breaks down - chromatin condenses to form chromosomes - homologous chromosomes pair up and cross over to form bivalents - spindle fibres assembled by centrioles and attached to centromeres of bivalents

Question 28

metaphase 1

Answer 28

- bivalents align on the metaphase plate/equator - independent assortment ( random which poles maternal and paternal chromosomes will face)

Question 29

anaphase 1

Answer 29

- spindle fibres contract - homologous chromosomes pulled to opposite poles

Question 30

recombiant chromatids

Answer 30

chromatids that have swapped alleles during crossing over

Question 31

chiasmata

Answer 31

the point where chromatids break and rejoin

Question 32

telophase 1

Answer 32

- nuclear envelope forms around chromosomes at opposite poles - chromosomes uncoil into chromatin - cytokinesis occurs

Question 33

prophase 2

Answer 33

- nuclear envelope breaks down - chromatin condenses into chromosomes - spindle fibres assemble from centrioles and attach to centromeres of chromosomes

Question 34

metaphase 2

Answer 34

- individual chromosomes align on the metaphase plate/equator - independent assortment (sister chromatids are not identical due to crossing over)

Question 35

anaphase 2

Answer 35

- spindle fibres contract - centromeres split and sister chromatids are pulled to opposite poles

Question 36

telophase 2

Answer 36

- nuclear envelope forms around chromatids at either pole - chromatids/chromosomes uncoil to form chromatin