Topic 2: Cell cycle and mitosis

Question 1

During which stage of the cell cycle does DNA replicate?

Answer 1

interphase/ s phase

Question 2

During which stage of the cell cycle does the cell divide to produce identical daughter cells?

Answer 2

Mitosis

Question 3

What would form if mitosis division became uncontrolled?

Answer 3

tumour

Question 4

What does mitosis produce and why?

Answer 4

Mitosis cell division involves one round of division and results in two diploid, genetically identical daughter cells. Mitosis is for growth and repair - for example in the clonal expansion of B cells in the humoral response

Question 5

State the four key stages of mitosis:

Answer 5

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase.

Question 5

Eukaryotic cells can divide by either:

Answer 5

• Mitosis
  -Meiosis

Question 6

Prokaryotic cells do not divide by mitosis. Name and describe the mechanism by which prokaryotic cells replicate

Answer 6

Binary fission involves the circular DNA and plasmids (if present) replicating and then the cytoplasm splitting to create two daughter cells. Each daughter cell has one copy of the circular DNA, but a variable number of plasmid copies.

Question 7

Describe how viruses replicate:

Answer 7

Viruses inject their nucleic acid into the host cells, which enables the replication of the virus particles.

Question 8

Describe the behaviour of chromosomes during each stage of mitosis. Include the key terms: spindle fibres, centromeres and chromatids. Prophase:

Answer 8

The chromosomes condense and become visible. In animal cells, the centrioles separate and move to opposite poles of the cell. The centrioles are responsible for creating spindle fibres which are released from both poles to create a spindle apparatus – these will attach to the centromere and chromatids on the chromosome in later stages. Plants have a spindle apparatus but lack the centrioles.

Question 9

Describe the behaviour of chromosomes during each stage of mitosis. Include the key terms: spindle fibres, centromeres and chromatids. Metaphase

Answer 9

The chromosomes align along the equator of the cell. The spindle fibres released from the poles now attach to the centromere and chromatid.

Question 10

Describe the behaviour of chromosomes during each stage of mitosis. Include the key terms: spindle fibres, centromeres and chromatids. Anaphase

Answer 10

The spindle fibres start to retract and pull the centromere and chromatids they are bound to towards the opposite poles. This causes the centromere to divide into two and the individual chromatids are pulled to each opposite pole. These separated chromatids are now referred to as chromosomes.
This stage requires energy in the form of ATP which is provided by respiration in the mitochondria.

Question 11

Describe the behaviour of chromosomes during each stage of mitosis. Include the key terms: spindle fibres, centromeres and chromatids. Telophase:

Answer 11

The chromosomes are now at each pole of the cell and become longer and thinner again.
The spindle fibres disintegrate, and the nucleus starts to reform.
The final stage in the cell cycle is when the cytoplasm splits in two to create the two new genetically identical cells.