cell division

Question 1

cell cycle

Answer 1

series of events which takes place as cell grows and divides

Question 2

interphase

Answer 2

phase of cell cycle where cell is NOT dividing (subdivided into growth and synthesis phases)

Question 3

G1

Answer 3

rapid growth phase

• ATP production
• manufacture of new organelles and proteins

Question 4

S

Answer 4

• DNA duplication

Question 5

G2

Answer 5

• cell growth
• rapid ATP production
• chromosomes checked for errors and repaired

Question 6

mitosis

Answer 6

nuclear division

Question 7

checkpoint 1 (G1)

Answer 7

ensures cell can enter S phase

• cell size
• nutrients
• growth factors
• DNA damage

Question 8

checkpoint 2 (G2)

Answer 8

ensure cell is ready for mitosis

• cell size
• DNA damage/ replication errors

Question 9

prophase MITOSIS

Answer 9

1. chromatin fibres condense into chromosomes which are now visible
2. nucleolus disappears
3. nuclear envelope disintegrates
   (in animal cells centrioles migrate to opposite poles)
4. spindle fibres form
5. spindle fibres attach to centromeres

Question 10

metaphase MITOSIS

Answer 10

1. chromosomes moved by spindle to cell equator

2. chromosomes held in place

Question 11

anaphase MITOSIS

Answer 11

1. centromeres divide
2. shortening spindle fibres cause chromatids to be pulled to different poles of the cell
   (characteristic V shape, as they are pulled through cytosol)

Question 12

telophase MITOSIS

Answer 12

1. nuclear envelope reforms
2. nucleolus reforms
3. chromosomes uncoil
4. spindle disintegrates

Question 13

cytokinesis

Answer 13

animals
- cleavage furrow forms and ingresses

plants
- cell plait laid down in the centre

Question 14

prophase 1 MEIOSIS

Answer 14

1. chromatin fibres condense into chromosomes now visible
2. nuclear membrane disintegrates
3. homologous chromosomes pair up in synapsis
   (1 pair = 1 bivalent, 2 chromatids joined at chiasma)
   - crossing over of genetic material
4. centrioles migrate to poles
5. spindle fibres form

Question 15

metaphase 1 MEIOSIS

Answer 15

1. bivalents pulled to the centre of the cell, attached by centromeres
   (independent assortment)

Question 16

anaphase 1 MEIOSIS

Answer 16

1. spindle fibres pull homologous chromosomes to poles of the cell

Question 17

telophase 1 MEIOSIS

Answer 17

1. nuclear envelope reforms

2. chromatin fibres uncoil

Question 18

prophase 2 MEIOSIS

Answer 18

1. chromatin fibres condense
2. nuclear envelope disintegrates
3. spindle fibres form

Question 19

metaphase 2 MEIOSIS

Answer 19

2. chromosomes line up at the centre of the cell

Question 20

anaphase 2 MEIOSIS

Answer 20

1. centromeres divide

2. chromatids pulled to poles of the cell

Question 21

telophase 2 MEIOSIS

Answer 21

1. nuclear envelope forms
2. chromatin fibres uncoil
   centrioles replicate
3. spindle fibres disintegrate

Question 22

genetic variation in meiosis

Answer 22

• independent assortment of bivalents
• separation of bivalents
• crossing over of segments in synapsis
• haploid cells (gamete only carries 1 allele for the particular gene)

ALL produce large numbers of allele combinations

Question 23

differentiation

Answer 23

• process by which cells specialise to take on different roles in tissues and organs
• when cells differentiate they become adapted to their specific role

Question 24

stem cell

Answer 24

undifferentiated cell able to express all of its genes and divide by mitosis

Question 25

embryonic adult/tissue umbilical cords meristematic tissue

Answer 25

totipotent source - embryo pluripotent source - bone marrow multipotent source - umbilical cord pluripotent source - tips of shoots, roots

Question 26

yeast cell division

Answer 26

reproduce asexually by budding - swelling of cell surface - creates a bulge - nucleus moves into the bulge - bulge is pinched off/ breaks off

Question 27

homologous chromosomes

Answer 27

- 1 maternal + 1 paternal chromosome - carry the same genes - same/different alleles - joined at centromere