12 - The Cell Cycle and Cell Division (C2)

Question 1

What is the name of the region where chromatids join?

Answer 1

Centromere

Question 2

What does haploid mean?

Answer 2

Having 1 complete set of chromosomes

Question 3

What does diploid mean?

Answer 3

Having 2 complete sets of chromosomes

Question 4

What is cytokinesis?

Answer 4

The division of the cytoplasm to form 2 daughter cells

Question 5

What is the difference between interphase in meiosis 1 and 2?

Answer 5

In meiosis 2 DNA doesn’t replicate

Question 6

What happens during interphase of mitosis / meiosis 1?

Answer 6

• DNA replicates
• Cell organelles duplicate
• Cell builds the proteins needed for division

Question 7

Why are interphase and cytokinesis not considered as part of mitosis / meiosis 1?

Answer 7

Because the chromosomes aren’t visible

Question 8

What happens in prophase of mitosis?

Answer 8

• Chromosomes condense and appear as ‘X’ shaped structures
• Centrioles move to poles
• Spindle fibres start to develop

Question 9

What is the order of stages in mitosis and meiosis?

Answer 9

• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

Question 10

What happens in metaphase of mitosis?

Answer 10

• Chromosomes move to and line up on equator

- Spindle fibres connect between centriole and centromea

Question 11

What happens in anaphase of mitosis?

Answer 11

• Spindle fibres shorten
• 1 chromatid is pulled from each chromosome to each pole
• Separating the centromea

Question 12

What happens in telophase of mitosis?

Answer 12

• Chromosomes uncoil (decondense)
• Spindle fibres break down
• Endo-membranes reform

Question 13

When does prophase occur in mitosis?

Answer 13

As soon as chromosomes become visible

Question 14

When does metaphase occur in mitosis?

Answer 14

As soon as nuclear envelope breaks down

Question 15

When does anaphase occur in mitosis?

Answer 15

As soon as chromatids start to separate

Question 16

When does telophase occur in mitosis?

Answer 16

As soon as chromatids reach the poles

Question 17

What happens in prophase of meiosis 1 / 2?

Answer 17

• Chromosomes condense and line up in their homologous pairs
• Chromatids cross over and exchange genetic information between homologous pairs
• Centrioles move to poles and spindle fibres appear

Question 18

What happens in metaphase of meiosis 1 / 2?

Answer 18

• Chromosomes move to and line up in their pairs on the equator
• Spindle fibres connect between centromeas and centrioles

Question 19

What happens in anaphase of meiosis 1 / 2?

Answer 19

• Spindle fibres shorten
• 1 chromosome from each pair is pulled to each pole
• Centromeas don’t separate

Question 20

What happens in telophase of meiosis 1 / 2?

Answer 20

Usually:

• Chromosomes uncoil
• Endomembranes reform
• Spindle fibres break down

Question 21

Why does mitosis happen?

Answer 21

To produce genetically identical cells for growth and repair, and asexual reproduction

Question 22

Why does meiosis happen?

Answer 22

To produce cells with half the number of chromosomes which are gametes for sexual reproduction

Question 23

What causes independent assortment?

Answer 23

The random orientation of chromosomes pairs at metaphase 1 and of chromatids at metaphase 2

Question 24

What causes recombination due to crossover?

Answer 24

• Homologous chromosomes cross over during prophase 1. Their chromatids form chiasmata which move towards the ends leading to the exchange of genes
• If 2 genes are on the same chromosome some gametes will inherit the parental combinations, whilst others will be recombinant

Question 25

What causes chromosome mutation, leading to Polysomy (Down's syndrome) or Polyploidy?

Answer 25

Unequal separation of chromosomes at anaphase 1 or 2

Question 26

What causes chromosome mutation, leading to duplication or inversion?

Answer 26

A failure of DNA being exchanged equally during cross over at prophase 1

Question 27

What causes point mutation during meiosis?

Answer 27

Mistake in DNA replication (base pairing) during interphase

Question 28

What happens in phase M?

Answer 28

- DNA is condensed and splits | - 4 phases: prophase, metaphase, anaphase, telophase

Question 29

What happens in phase G1?

Answer 29

Cell grows and develops into a mature cell

Question 30

What happens in phase S?

Answer 30

The cell duplicates the DNA and centromere

Question 31

What happens in phase G2?

Answer 31

The cell prepares for mitosis. It's still growing and making proteins and organelles

Question 32

What are G1, S and G2 collectively called?

Answer 32

Interphase

Question 33

What are differences between mitosis in animal cells and plant cells?

Answer 33

ANIMAL - Cell becomes rounded before mitosis - Centrioles present - Cleavage furrow, which develops from outside inwards - Spindle fibres degenerate at telophase - Occurs in epithelia, bone marrow etc PLANT - No shape change - Centrioles absent - Cell plate, which develops from centre outwards - Spindle fibres remain throughout new cell wall formation - Occurs in meristems

Question 34

How is prophase 2 different to prophase 1?

Answer 34

At prophase 2 the centrioles separate and organise a new spindle at right angles to the old spindle