Cell cycle, Mitosis and Meiosis

Question 1

What happens during G1

Answer 1

Protein synthesis
Replication of organelles
cell increases in size

Question 2

What happens during S

Answer 2

Chromosomes are duplicated / DNA is replicated

Question 3

What happens during G2

Answer 3

Increase in cell size
increase in energy stores
Duplicated DNA from S phase is checked for errors

Question 4

What is G0

Answer 4

When the cell leaves the cell cycle permanently or temporarily.

Question 5

Why would the cell leave the cycle?

Answer 5

DNA may be damaged - The cell should no longer divided, so the cell enters a state of arrest.

Age - As you get older you have more cells, therefore by leaving the cycle they can’t replicate, this decreases the chances of problems such as arthritis

Differentiation - Once a cell has specialised it may no longer divided and re-enter the cell cycle.

Question 6

What is the G1 checkpoint

Answer 6

Makes sure the cell is the correct size
Makes sure the cell has the correct nutrients
Checks DNA for damage before entering S phase

Question 7

What is the G2 checkpoint

Answer 7

Makes sure the cell is the correct size

Checks if the replicated DNA has any errors after S phase

Question 8

What is the spindle assembly checkpoint

Answer 8

Checks the spindle fibres are connected to the chromosomes

Question 9

Uses of mitosis

Answer 9

Asexual reproduction
Growth of Multicellular organisms
Tissue repair

Question 10

What does it produce?

Answer 10

Two identical daughter cells

Question 11

What occurs during S phase (mitosis)

Answer 11

The chromatids are. separated via the centromere they must stay together so each can go into a daughter cell

Question 12

Acronym for the stages of mitosis

Answer 12

People (Prophase)
Must (Metapahse)
Attack (Anaphase)
Teachers (Telophase)

Question 13

What happens during Prophase of mitosis

Answer 13

1. Chromatin begins to coil and condenses to form chromosomes and become visible under the microscope
2. The nuclear membrane breaks down
3. Microtubules form spindle fibers
4. Centrioles move to opposite ends of the poles
5. Spindle fibres connect to the centromeres of the chromatins

Question 14

What happens during Metaphase of mitosis

Answer 14

Chromosomes are pulled to the centre of the cell to form a line called the Metaphase plane where is stays until Anaphase

Question 15

What happens during Anaphase of mitosis

Answer 15

The centromeres holding the chromatids together pull the chromatids to opposite sides of the cell. They form a ‘V’ like shape making the easily identifiable

Question 16

What happens during Telophase of mitosis

Answer 16

1. The two new set of chromosomes assemble at the end of each pole, and a nuclear envelope forms around them.
2. The chromosomes uncoil and a nucleolus forms
3. Cytokinesis begins

Question 17

What is cytokinesis

Answer 17

The actual split off the cell.

Question 18

What happens in animal cells during cytokinesis

Answer 18

1. A cleavage forms at the centre of the cell.

2. The cell surface membrane is pulled inwards by. the cytoskeleton until it fuses in the middle forming two cells.

Question 19

What happens in Plant cells during cytokinesis

Answer 19

1. Vesicles from ht Golgi form where. the metaphase plate was.
2. The vesicles eventually fuse together.
3. A new cell wall is formed essentially making a new cell.

Question 20

How many chromosomes are present during mitosis

Answer 20

There are 46 chromosomes throughout however during prophase there are 96 chromatids.

Question 21

Uses of meiosis

Answer 21

The formation of gametes / sex cells

Question 22

What is a homologous chromosome

Answer 22

A matching pare of chromosomes, one inherited from each parent.

Question 23

What does diploid mean

Answer 23

The normal number of chromosomes (46)

Question 24

What does haploid mean

Answer 24

Half the number of normal chromosomes (23)

Question 25

What is Meiosis 1

Answer 25

The first division = reduction division

Homologous chromosomes go into two cells

Question 26

What is Meiosis 2

Answer 26

Secondary division = similar mitosis

Everything is halved again

Question 27

What happens during Prophase 1 of meiosis and what is the difference

Answer 27

Chromosomes condense
Nuclear envelope dissolves
Nucleolus disappears
Spindle begins to form

Difference:
Homologous chromosomes pair up forming bivalent, when the chromosomes flow through their liquid they entangle.

Question 28

What happens during Metaphase 1 of meiosis and what is the difference

Answer 28

Chromosomes are pulled to the middle the cell and form along the metaphase plate

Differences:
Homologous chromosomes form up against. the metaphase line instead of individual chromosomes.
The position of the chromosomes are random, this is called independent assortment.

Question 29

What happens during Anaphase 1 of meiosis

Answer 29

The homologous chromosomes are separated and are pulled to the opposite poles via spindle fibres
The bivalent entangled chromosomes are pulled. apart. and re join at the chiasma, this is an exchange of DNA

Question 30

What happens during Telophase 1 of meiosis

Answer 30

Chromosomes assemble together
Nuclear membrane form around them
The chromosomes uncoil.
Cytokinesis occurs

Question 31

What happens during Prophase 2 of meiosis

Answer 31

Chromosomes condense
Nuclear membrane breaks down
Spindle fibres form

Question 32

What happens during Metaphase 2 of meiosis

Answer 32

Individual chromosomes area aligned along the metaphase plate like in mitosis

Question 33

What happens during Anaphase 2 of meiosis

Answer 33

The individual chromosomes are pulled to opposite ends of the poles.

Question 34

What happens during telophase 2 of meiosis

Answer 34

Nuclear membrane forms around the chromosomes
Chromosomes uncoil and nucleolus forms
Cytokinesis coccus forming 4 genetically different daughter cells.