Cell division: mitosis and the cell cycleIB MYP Biology: Subtopic test

1. 1
   A child falls over and cuts her knee. Over the next week the cut heals, because the skin cells next to the wound divide to replace the cells that were damaged.

   (a)

   What is the result of one round of mitosis?

   [1 mark]

   • AFour cells that are genetically different from the parent cell
   • BTwo cells that are genetically identical to the parent cell
   • CTwo cells with different genetic information from each other
   • DOne large cell with two nuclei

   (b)

   What happens to the DNA in a cell before the nucleus divides?

   [1 mark]

   • AIt is copied
   • BIt is destroyed
   • CIt is halved
   • DIt is turned into protein

   (c)

   Explain why mitosis is needed for the cut to heal.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A spider plant grows small plantlets on long stems. When these are planted in soil, each plantlet grows into a new plant that looks identical to the parent plant.

   (a)

   Why are the new plants identical to the parent plant?

   [1 mark]

   • AThey are produced by fertilisation, which mixes genetic information
   • BMitosis halves the DNA in the cells of the plantlet
   • CThey grew in the same soil as the parent
   • DThey are produced by mitosis, which makes genetically identical cells

   (b)

   What is this type of reproduction called?

   [1 mark]

   • ASexual reproduction
   • BFertilisation
   • CAsexual reproduction
   • DPollination

   (c)

   State two other uses of mitosis in a living organism, apart from asexual reproduction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student wants to find out whether cells at the tip of an onion root divide more often than cells further up the root. She cuts a thin slice from the tip of the root and another slice from 2 cm higher up. She stains each slice to show the nuclei and views it under a light microscope, counting how many cells are dividing.

   (a)

   State a testable hypothesis for the investigation, with a scientific reason, and identify the independent variable.

   [3 marks]

   (b)

   In one field of view she counted 12 dividing cells out of 80 cells at the tip, and 3 dividing cells out of 75 cells from 2 cm higher up. Calculate the percentage of dividing cells for each position, describe the trend and evaluate whether the results support the hypothesis.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Skin cancer happens when skin cells divide out of control and form a tumour. A country's health ministry is considering a free screening programme in which every adult has their skin checked each year. Cancers found early can usually be treated successfully, but the programme would cost millions, and some checks would wrongly suggest cancer in healthy people.

   (a)

   Describe how mitosis normally happens and explain how it can lead to cancer.

   [6 marks]

   (b)

   Discuss whether the government should introduce a national skin cancer screening programme.

   [6 marks]

   Total for question 4: 12 marks

End of questions