2.1 Cell Division

Figure 1 shows the quantity of DNA found in the nucleus of a human cell throughout the cell cycle.

Figure 1

Identify what is happening during stage B in Figure 1. Explain your answer.

Figure 1 shows two complete cell cycles. 50% of the cell cycle is spent in stage A and 30% is spent moving through stage C. 

Calculate how long the cells spend in stage B of the cell cycle.

How many chromatids would be found in the nucleus of this human cell during stage B?

Describe the stages of the cell cycle.

When a cell divides by mitosis, it produces identical daughter cells, however, when a zygote divides by mitosis, it develops into an embryo and then a foetus.

Explain how the process of mitosis can produce a whole organism from a single cell.

Compare and contrast the processes of mitosis and meiosis.

Initially, before a cell can divide, it needs to prepare for division by replicating DNA within the nucleus. During this time, there are no visible chromosomes. 

Figure 1 shows a cell sample taken from plant tissue. The cell cycle in this plant tissue takes 20 hours.

Figure 1

Calculate how long cells remain in the preparation stage before cell division occurs.

Some scientists studied mitosis in yeast cells. Figure 1 shows the concentration of DNA and the number of yeast cells over a 12 hour period.

Figure 1

Describe and explain the shape of the curve for the number of yeast cells between 2 and 8 hours.

One cell cycle in Figure 1 from part (a) takes 6 hours.

Calculate the percentage of time taken by mitosis in one cell cycle.

Figure 2 shows cells in two stages of division.

Figure 2

Describe the changes that occur in the cell between image X and image Y.

Cancer cells originate from healthy cells where the cell cycle is not being controlled normally. This can lead to uncontrolled cell division and the formation of tumours. Drugs used to destroy cancer cells also cause damage to healthy cells, although are more effective against the cancer cells.

Figure 1 shows the effect of a chemotherapy cancer treatment on the number of healthy and cancerous cells over a 12-week time period.

Calculate how many more cancer cells than healthy cells were destroyed after the first treatment.

Give your answer in standard form.

With reference to the data in Figure 1, identify a time period in which the cancer cells were dividing by mitosis. 

Another treatment for cancer patients is to receive a stem cell transplant from a donor. The process includes the following steps:

1. The patient is given a high dose of chemotherapy
2. Stem cells are taken from the bone marrow of a closely-related individual (with similar tissue type and genotype)
3. Stem cells are introduced into the patient
4. The patient is monitored for after-effects of the transplant

With reference to the data in Figure 1 and the information provided here, suggest why a high dose of chemotherapy might be necessary.

With reference to the process described in part (c), suggest an issue that might be associated with receiving a stem cell transplant which requires careful monitoring of the patient after the procedure (stage 4).

Outline two events that occur during the mitotic stage of prophase within a cell.

A cell undergoing mitosis is described as 'diploid'.

Explain the meaning of the term 'diploid'.

Each cell in an embryo is undergoing mitosis at a rapid rate as the embryo grows in its mother's womb. 

Figure 1 below gives approximate numbers of cells in a human body at various stages of its development.

Figure 1

Using the data from Figure 1, calculate the rate per day of new cell production between 7 and 10 days after fertilisation.

Referring to the data in Figure 1, calculate the percentage increase in number of cells between a 20-week foetus and a newborn baby.

Outline the events that take place in interphase of the cell cycle. 

A body cell from an animal contains a fixed amount of DNA, given in Figure 1 as 10 arbitrary units.

Figure 1

Complete the empty cells in Figure 1.

Give an explanation for your answer to the lowest row of the table (sperm cell) in (b)  

Mitosis was first referred to as 'cell division', even though cells multiply in number by this process. 

State a reason why the process was first termed 'cell division' rather than 'cell multiplication'.

Figure 1 shows four stages of mitosis, labelled P, Q, R and S.

(2)

Mitosis and meiosis are processes that produce new cells.

Compare the outcomes of mitosis and meiosis.

A student investigated mitosis in the root tip of a garlic plant.

Figure 1 shows a root cell in a stage of mitosis.

Figure 1