Mitosis And The Cell Cycle

Question 1

What stages does the cell cycle comprise of?

Answer 1

• interphase
• nuclear division (mitosis or meiosis)
• cytokinesis

Question 2

What stages happen within interphase?

Answer 2

• G1
• S
• G2

Question 3

What happens during the stage G1?

Answer 3

Growth

Question 4

What happens during the stage S?

Answer 4

DNA synthesis.

Question 5

What happens during the stage G2?

Answer 5

Growth and preparation for mitosis.

Question 6

What happens during the M (mitosis) stage?

Answer 6

Mitosis (cell division)

Question 7

What is interphase?

Answer 7

Interphase is the longest stage in the cell cycle. It is when the organelles double, the cell grows and then DNA replicates.

Question 8

What is nuclear division?

Answer 8

Nuclear division can be either mitosis, creating two identical diploid cells, or meiosis, creating four genetically different haploid cells. Mitosis creates cells with identical DNA for growth and repair, where as meiosis creates gametes.

Question 9

What is cytokinesis?

Answer 9

It is the final stage. It is the division of the cytoplasm to create new cells.

Question 10

What are the four key stages of mitosis?

Answer 10

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 11

What happens during prophase?

Answer 11

• In this stage, 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 12

What happens during Metaphase?

Answer 12

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

Question 13

What happens during Anaphase?

Answer 13

• 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 in two and the individual chromatids are pulled to each opposite pole.
• These separated chromatids and now referred to as chromosomes.
• This stage requires energy in the form of ATP which is provided by respiration in the mitochondria.

Question 14

What happens during Telophase?

Answer 14

• 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.v

Question 15

How do you calculate mitotic index?

Answer 15

mitotic index = the number of cells in mitosis x 100
the total number of cells