Topic 2-cells- The cell cycle

Question 1

What is Interphase in the cell cycle?

Answer 1

-Interphase is the longest stage in the cell cycle
-Interphase is when the organelles double, the cell grows and DNA replicates.
-ATP content is increased, which provides energy needed for cell division

Question 2

What is Nuclear Division, in the cell cycle?

Answer 2

-Nuclear division can either be mitosis, creating 2 identical diploid cells, or meiosis, creating 4 genetically different haploid cells.
- Mitosis creates cells with identical DNA for growth and repair, whereas meiosis creates gametes.

Question 3

What is Cytokinesis, in the cell cycle?

Answer 3

Cytokinesis is the final stage of the cell cycle and involves the division of the cytoplasm to create the new cells.

Question 4

What happens in the G1 phase of Interphase, in the cell cycle?

Answer 4

During G1, the cell grows and new organelles and proteins are made

Question 5

What happens in S phase of Interphase, during the cell cycle?

Answer 5

-During S phase, DNA is synthesised.
-The cell replicates DNA, ready to divide by mitosis

Question 6

What happens in the G2 phase of Interphase, in the cell cycle?

Answer 6

-The cell grows and prepares for mitosis.
- Proteins needed for cell division are made
- The DNA replicated in S phase is checked for any mutations. The cell is destroyed, if any mutations detected to prevent harm.

Question 7

What does Mitosis produce?

Answer 7

2 genetically identical diploid cells

Question 8

How many rounds of cell division take place in Mitosis?

Answer 8

1

Question 9

What is Mitosis needed for?

Answer 9

-Mitosis is needed for growth and repair of eukaryotic cells.
- example: the clonal expansion of B cells in the humoral immune response.

Question 10

What is the order of the stages of Mitosis?

Answer 10

Prophase
Metaphase
Anaphase
Telophase

Question 11

Describe what happens in Prophase, in Mitosis

Answer 11

-Chromosomes condense and become visible- chromatin condenses into chromosomes
-nuclear envelope breaks down and chromosomes lie free in cytoplasm
- In animals, centrioles separate and move to opposite poles of cell
- The centrioles responsible for creating spindle fibres are released from both poles to create spindle apparatus. These attach to centromere and chromatids on chromosome in later stages.
- nucleolus disappears.

Question 12

Describe what happens in Metaphase in Mitosis

Answer 12

• Chromosomes align along centre of cell- chromosomes line up along metaphase plate.
• spindle fibres released from the poles and formed by centrioles, now attach to centromere and chromatid

Question 13

Describe what happens in Anaphase in Mitosis.

Answer 13

-Spindle fibres start to retract and pull the centromere and chromatids they are attached to, towards opposite poles of cell.
- This causes centromere to divide in 2, and the individual chromatids are pulled to each opposite pole
- separated chromatids are now chromosomes
- This stage requires energy in the form of ATP which is provided by respiration in the mitochondria.

Question 14

Describe what happens in Telophase in Mitosis

Answer 14

-The chromosomes are now at each pole of cell and become longer and thinner again (not as visible)- chromosomes unwind into chromatin.
- The spindle fibres disintegrate and the nuclear envelope starts to reform
- the final stage in the cell cycle is when the cytoplasm splits in two, to create the 2 new genetically identical cells- CYTOKINESIS- starts in anaphase and ends in telophase. - myosin II and actin filament ring contract to cleave cell in two.