Mitosis

Question 1

In what two ways can cell division take place?

Answer 1

By mitosis or meiosis.

Question 2

What does mitosis produce?

Answer 2

It produces two daughter cells that have the same number of chromosomes as the parent cell and each other.

Question 3

What does meiosis produce?

Answer 3

This produces four daughter cells, each with half the number of chromosomes of the parent cell.

Question 4

Explain the structure of a chromosome.

Answer 4

A diploid chromosome contains two chromatids which are joined in the centre by the centromere.

Question 5

In mitosis do the daughter cells have the exact same copy of DNA as the parent cell?

Answer 5

Yes

Question 6

Do the two daughter nuclei have the same genetic make up is the parent nucleus?

Answer 6

Yes, unless there has been a mutation but this is very rare.

Question 7

What is interphase?

Answer 7

This is a period during which the cell is not dividing.

Question 8

What are the five stages of the cell cycle?

Answer 8

Interphase
Prophase
Metaphase
Anaphase
Telephase and cytokinesis

Question 9

In what stage do the chromosomes first become visible?

Answer 9

In prophase.

Question 10

What happens to the chromosomes in prophase?

Answer 10

The chromosomes become visible, first as long thin threads before thickening and shortening.

Question 11

What do animal cells contain?

Answer 11

To cylindrical organelles called centrioles, each of which move to the opposite ends of the cell in prophase.

Question 12

What moves to opposite ends of the cell in prophase?

Answer 12

The centrioles.

Question 13

Where do spindle fibres develop in prophase?

Answer 13

They develop from each of the centrioles.

Question 14

Where do the spindle fibres span in prophase?

Answer 14

They span the cell from pole to pole.

Question 15

What are the spindle fibres known collectively as in prophase?

Answer 15

There are collectively known as the spindle apparatus.

Question 16

Do plant cells develop a spindle apparatus in prophase?

Answer 16

Despite not having centrioles, plant cells do develop a spindle apparatus, this suggests that centrioles are not essential to spindle fibre formation.

Question 17

What happens to the nucleolus and the nuclear envelope in prophase?

Answer 17

The nucleolus disappears and the nuclear envelope breaks down; this leaves the chromosomes free in the cytoplasm of the cell.

Question 18

What draws the chromosomes to the equator of the cell in prophase?

Answer 18

The chromosomes are drawn towards the equator of the cell by the spindle fibres which are attached to the to the centromere.

Question 19

What happens in metaphase?

Answer 19

The chromosomes seem to be made up of two chromatids each of which holds an identical copy of DNA from the parent cell. The chromosomes are joined by the centromere which is attached to some microtubules from the poles and the chromosomes are pulled along the spindle apparatus and arrange themselves across the equator of the cell.

Question 20

What happens to the centromeres in anaphase?

Answer 20

The centromere divides into two.

Question 21

What pulls the individual chromatids apart in anaphase?

Answer 21

The spindle fibres pull the individual chromatids apart.

Question 22

Where do the chromatids move to in anaphase and what are they now referred to as?

Answer 22

The chromatids move rapidly to their respective opposite poles of the cell and are then referred to as chromosomes.

Question 23

What provides the energy for anaphase?

Answer 23

Mitochondria

Question 24

Where did the mitochondria gather round during anaphase?

Answer 24

They gather around the spindle fibres.

Question 25

What happens if cells are treated with chemicals that destroy the spindle?

Answer 25

The chromosomes remain at the equator and are unable to reach the poles.

Question 26

What happens in telophase?

Answer 26

The chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether, only leaving a widely spread chromatin. The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form.

Question 27

What happens to the spindle fibres in telophase?

Answer 27

The spindle fibres disintegrate.

Question 28

What happens to the nuclear envelope and the nucleolus in telophase?

Answer 28

The nuclear envelope and nucleolus re-form.

Question 29

What happens in cytokinesis?

Answer 29

The cytoplasm divides.

Question 30

What is cell division in prokaryotic cells known as?

Answer 30

Binary fission

Question 31

What happens in binary fission?

Answer 31

The circular DNA molecule replicates and both copies attach to the cell membrane. The plasmids also replicate. The cell membrane begins to grow between the DNA molecules and begins to pinch inwards, dividing the cytoplasm into two. A new cell wall forms between the two molecules of DNA, dividing the original cell into two identical daughter cells, each with a single copy of the circular DNA and a variable number of copies of the plasmids.

Question 32

Can viruses go through cell division?

Answer 32

No

Question 33

Why can't viruses go under cell division?

Answer 33

This is because they are non-living.

Question 34

How do viruses replicate?

Answer 34

They attach to the host cell with the attachment proteins on their surface. They then inject the nucleic acid into the host cell. The genetic information on the injected viral nucleic acid then provides the "instructions" for the host cell's metabolic processes to start producing the viral components, nucleic acid, enzymes and structural proteins, which are then assembled into new viruses.

Question 35

What 3 things is mitosis important for?

Answer 35

Growth Repair Reproduction

Question 36

How does mitosis aid growth?

Answer 36

When two haploid cells fuse together to form a diploid cell, it has all the genetic information needed to form the new organism. If the new organism is to resemble its parents, all the cells that grow from this original cell must be genetically identical. Mitosis ensures that this happens.

Question 37

How does mitosis aid repair?

Answer 37

If cells are damaged or die it is important that the new cells produced have an identical structure and function to the ones that have been lost.

Question 38

How does mitosis aid reproduction?

Answer 38

Single-celled organisms divide by mitosis to give two new organisms. Each new organism is genetically identical to the parent organism.

Question 39

Suggest an advantage and a disadvantage of having offspring that are genetically identical to their parents.

Answer 39

An advantage of this is that as the genetic make up of the parent has enabled it to survive and reproduce its offspring have the same genetic make up so they are also likely to survive and reproduce. A disadvantage is that genetic variety is limited limited this means that if environmental conditions change the species may not have individuals with the necessary genes to survive in the new conditions and if it to fails to adapt it could become extinct.