Cell Division

Question 1

Why does cell division occur in multicellular organisms?

Answer 1

Cell division allows them to grow and replace damaged or worn out cells.

Question 2

What are the types of cell division in eukaryotic cells?

Answer 2

Mitosis and meiosis are the two types of cell division.

Question 3

What is meiosis?

Answer 3

It is a type of cell division that produces 4 identical haploid (1 complete set of chromosomes) daughter cells (gametes). It takes place in reproductive organs for sexual reproduction.

Question 4

What is mitosis?

Answer 4

It is a type of cell division that produces 2 genetically identical diploid (2 complete sets of chromosomes) daughter cells. It is used to grow tissues, replace cells, repair damaged tissue, form clones of white blood cells and form cancerous tumours.

Question 5

What is the cell cycle?

Answer 5

It is a process cells go through in order to divide and multiply.

Question 6

What are the stages of the cell cycle?

Answer 6

1. Interphase (includes G1, S and G2 phases)
2. Mitosis (includes prophase, metaphase, anaphase and telophase)
3. Cytokinesis

Question 7

What happens during interphase?

Answer 7

Interphase takes up 90% of the cell cycle. In this phase, the cell grows and DNA is uncondensed and doubled. Organelles are replicated and also, the amount of ATP is increased to produce enough energy for cell division.

Question 8

What happens in each stage of interphase?

Answer 8

1. G1 - the cell elongates and new organelles and proteins are made.
2. S (synthesis) - the cell replicates its DNA
3. G2 - the cell keeps elongating and proteins needed for cell division are made.

Question 9

What is cytokinesis?

Answer 9

This is the final stage of the cell cycle where the cytoplasm divides and two separate, identical cells are formed.

Question 10

What is the structure of chromosomes?

Answer 10

Chromosomes are made of one (during mitosis) or two chromatids joined in the middle by a centromere.

Question 11

What order are the stages of mitosis?

Answer 11

The stages can be remembered by IPMAT.
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 12

What happens during prophase?

Answer 12

While the DNA is uncondensed in interphase, the chromosomes condense in prophase (DNA is tightly coiled around proteins called histones) and become visible. The nucleolus disappears and nuclear envelope begins to break down. The centrioles begin to produce spindle fibres.

Question 13

What happens during metaphase?

Answer 13

By now, the nuclear membrane has disappeared and spindle fibres attach to the centromere of the chromosomes. The chromosomes are pulled to the equator (middle) of the cell and line up there.

Question 14

What happens during anaphase?

Answer 14

The spindle fibres contract and the centromere of each chromosome splits in half, pulling its chromatids to opposite poles.

Question 15

What happens during telophase?

Answer 15

The nuclear envelope begins to reform around each group of new chromosomes. The spindle fibres disappear and the chromosomes begin to uncoil.

Question 16

How do you calculate the time taken for stages of mitosis to occur?

Answer 16

1. To calculate this, you need the number of cells undergoing mitosis, the total number of cells and how long the cell cycle takes.
2. Calculate the proportion of cells in a specific phase of mitosis.
3. Convert the cell cycle time to units required for the answer.
4. Calculate the proportion of time spent in this phase compared to the whole cycle.