1. Within mitosis there are a number of stages. List these stages in order.
Answer
Prophase, metaphase, anaphase, telophase.
2. Why is it so important that mitosis is a controlled process ?
Answer
Can lead to cancer.
3. Describe and explain the difference between chromosome A and B in the figure below.
Answer
Chromosome A is shown before replication. Chromosome B is shown after replication and consists of two identical sister chromatids attached by a centromere.
4. The figure below shows a field of view in an optical microscope of cells in different stages of the cell cycle. Calculate the mitotic index.
Answer
The mitotic index is 20/75
5. Explain how we could ensure that the calculation of mitotic index was as reliable as possible.
Answer
Select multiple fields of view, ensuring that they are chosen at random. Then calculate the mean of the different mitotic indexes.
6. The figure below shows the mean distances between sister chromatids in mitosis. Describe and explain what is happening in the cell during stages A, B and C.
Answer
At A, the distance is zero because the sister chromatids are attached to each other during prophase and metaphase. At B, the distance between chromatids increases as the sister chromatids separate and move to opposite poles of the cell during anaphase. The chromatids are pulled to opposite poles by spindle fibres. At C, the chromatids (daughter chromosomes) have reached the poles of the cell.
7. Indole sulphonamide is a drug used to treat cancer. It works by stopping spindle fibres forming. Explain why this would mean that a cancer cell would be unable to complete the cell cycle.
Answer
Chromosomes would be unable to line up at the equator, and sister chromatids would not be able to separate to opposite poles.
8. Name some processes that occur in a cell during interphase.
Answer
DNA replication, respiration, protein synthesis, photosynthesis, replication of organelles.
9. Fludarabine is a drug that inhibit the cell cycle and is similar in shape to an adenine nucleotide. Explain how fludarabine inhibits the cell cycle.
Answer
Fludarabine is incorporated into new DNA instead of adenine nucleotides, resulting in faulty or non-functional DNA. As a consequence, the cell cannot enter mitosis (prophase).
10. The figure below shows a cell during mitosis. Describe what will happen in this cell in the next stage of mitosis.
Answer
New nuclear membrane forms and chromosomes condense out.
11. Describe how a student could recognise that a cell is in metaphase.
Answer
Chromosomes are aligned along the equator (middle) of the cell and are attached to spindle fibres.