cell division

Question 1

What is G0? Why might a cell enter G0?

Answer 1

The resting phase, in which the cell leaves the cycle temporarily or permanently
When a cell is specialized it no longer needs to divide, hence entering G0

Question 2

Which cells DON’T divide?

Answer 2

DNA damaged cells and senescent cells

Question 3

What happens at each checkpoint of the cell cycle? (4, 3, 2)

Answer 3

G1 checkpoint checks for:
cell size, nutrients, growth factors, DNA damage

G2 checkpoint checks for:
cell size, DNA replication, DNA error

Spindle assembly checkpoint checks for:
all chromosomes attached to spindles and being aligned

Question 4

What happens at G1 phase? (3)

Answer 4

• proteins synthesised
• organelles replicated
• cell enlarges

Question 5

What happens at synthesis phase?

Answer 5

DNA replicated

Question 6

What happens at G2 phase? (3)

Answer 6

• energy stores are increased
• DNA checked for errors
• cell enlarges

Question 7

True or false- chromatids are singular structures of DNA and chromosomes are the X ones

Answer 7

False- chromatids and chromosomes are the same thing! X pairs are typically called sister chromatids and when they split into singular structures they are then chromosomes

Question 8

What is the role of the centromere in mitosis? (3)

Answer 8

• holds chromatids together
• attaches chromatids to spindle fibres
• allows chromatids to be separated

Question 9

MITOSIS: Prophase (3)

Answer 9

• chromatins condense to form chromosomes/chromatids
• nuclear envelope breaks down
• spindle fibres form at poles

Question 10

MITOSIS: Metaphase

Answer 10

chromosomes lined up at metaphase plate (equator)

Question 11

MITOSIS: Anaphase (2)

Answer 11

• centromeres divide
• spindle fibres contract to separate sister chromatids

Question 12

MITOSIS: Telophase (3)

Answer 12

-chromatids/chromosomes reach poles and coil
- nuclear envelope reforms
- nucleolus formed

Question 13

MEIOSIS I: Prophase I

Answer 13

Chromosomes pair up into BIVALENTS + CROSS OVER

Question 14

MEIOSIS I: Metaphase I

Answer 14

Homologous pairs (4 chromatids) line up via INDEPENDENT ASSORTMENT

Question 15

MEIOSIS I: Anaphase I

Answer 15

Chromosomes are pulled to poles + chromatids become RECOMBINANT (as DNA breaks off and rejoins at CHIASMATA)

Question 16

How is MEIOSIS II different to mitosis? (2)

Answer 16

• results in 4 genetically different, haploid cells
• recombinant chromatids don’t need to pair up and can line up as is

Question 17

Functions of 4 types of tissues

Answer 17

• Connective: holds tissues together + transport medium
• Muscular: contracts
• Nerve: transmits electrical impulses
• Epithelial: covers internal and external body surfaces

Question 18

True or false- all cells have a different part of the human genome

Answer 18

False- all cells share an identical genome but it is the activation of genes that cause differentiation

Question 19

3 adaptations of erythrocytes

Answer 19

• flattened biconcave shape
• no nuclei
• flexible (to squeeze thru capillaries)

Question 20

4 adaptations of sperm

Answer 20

• acrosome (contains lysozymes)
• flagellum
• many mitochondria
• streamlined

Question 21

2 adaptations of neutrophil

Answer 21

• multi-lobed nucleus (move around quicker, change shape, extend cytoplasm to engulf)
• granular cytoplasm (contains many lysosomes)

Question 22

4 adaptations of palisade

Answer 22

• many chloroplasts
• rectangular
• thin walls
• large vacuole

Question 23

2 adaptations of root hair

Answer 23

• long extensions
• concentrated vacuole sap

Question 24

2 adaptations of guard cell

Answer 24

• thicker inner wall (on one side, so stoma can actually shut properly as shape isn’t symmetrical)
• ring of cellulose

Question 25

2 adaptations of squamous epithelium

Answer 25

• flattened cells
• permeable (for selective diffusion)

Question 26

2 adaptations of ciliated epithelium

Answer 26

• cilia
• goblet cells