Mitosis

Question 1

What is mitosis?

Answer 1

Eukaryotic cells have a well defined cell cycle of growth and division. The length of the cell varies ending with mitosis. Each phase involves specific activities and varies in length from one organism to another.

Question 2

What are the stages of the cell cycle?

Answer 2

G1 - Growth Phase 1, cells prepare for DNA replication.
S - synthesis, DNA replication occurs
G2 - Growth Phase 2, short gap before mitosis
M - mitosis, nuclear division relatively short

Question 3

What check chromosome for mutations?

Answer 3

Proof reading enzymes

Question 4

What is mitosis affected by?

Answer 4

The availability of nutrients.

Question 5

What might happen to chromosomes with mutations picked up by the proof reading enzymes?

Answer 5

They may undergo ‘suicide’ if there are harmful mutations this is known as apoptosis.

Question 6

How long does it take for bacterial cells to complete a cycle?

Answer 6

20 minutes

Question 7

Muscle cells never complete a cell cycle what is this called?

Answer 7

Terminal differentiation

Question 8

What can uncontrolled cell division by mitosis cause?

Answer 8

Cancer.

Question 9

Define mitosis?

Answer 9

Process by which a nucleus divides into two, each with an identical set of chromosomes. They are genetically identical.

Question 10

What are the four stages of mitosis?

Answer 10

Prophase, metaphase, anaphase and telophase.

Question 11

What happens before mitosis?

Answer 11

Interphase.

Question 12

Define interphase?

Answer 12

Stages G1, S and G, it’s the period of cell growth, cells prepare for nuclear division, genetic material is copied and checked for errors, new organelles and proteins are made.

Question 13

What occurs after mitosis?

Answer 13

Cytokinesis

Question 14

What occurs in interphase?

Answer 14

The cell is engaged in metabolic activity. The DNA duplicates during this phase to prepare for mitosis. Chromosomes are not clearly discerned in the nucleus although a dark spot may be visible called the nucleolus.

Question 15

What occurs in prophase?

Answer 15

Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nuclear membrane breaks down and the chromosomes can be seen to consist of two chromatids. These X shaped structures move along the spindle to the opposite poles of the cell.

Question 16

What happens in metaphase?

Answer 16

Chromosomes align along the middle of the spindle. This line is referred to as the equator. This organisation helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive a copy of each chromosome.

Question 17

What happens in anaphase?

Answer 17

The chromatids separate at the the centromere and move to opposite ends of the cell. They are pulled by the spindle. The separated chromatids can now be referred to as new chromosomes.

Question 18

What happens in telophase?

Answer 18

New membranes form around the daughter nuclei while the chromosomes disperse and are no longer visible under a light microscope.

Question 19

What happens in cytokinesis?

Answer 19

The cell physically divides in two.

Question 20

What occurs during G1?

Answer 20

Protein synthesis cell ‘grows’. Most organelles produced. Volume of cytoplasm increases, cell differentiation occurs, length of this stage depends on the internal and external factors. If a cell is not going to divide again it stays in this stage. DNA content = 20.

Question 21

What occurs during S?

Answer 21

DNA replicates, this must occur if mitosis is to take place. The cell enters this stage only if cell division is to follow. DNA content = 40.

Question 22

What occurs during G2?

Answer 22

Short gap before mitosis. Cytoskeleton of cell breaks down and the protein microtuble components begin to reassemble into spindle fibres. DNA content = 40

Question 23

What does DNA content = in cytokinesis?

Answer 23

DNA content = 20

Question 24

What happens if the treatment for cancer is too strong?

Answer 24

It would kill off too many healthy cells which can lead to death.

Question 25

Define tumour?

Answer 25

A tumour is a group of undifferentiated abnormal cells. These can get larger and compress with tissues and use nutrients from the body. These cells can break off to form secondary tumours in other parts of the body.

Question 26

How is cancer caused?

Answer 26

Carcinogens such as tar and uv radiation causes mutations in the DNA of the cell. These mutations are changes in the nucleotide sequence of DNA this may happen via insertion, deletion or the order may change.