Cell division and growthIB MYP Sciences: Subtopic test

1. 1
   A student in Lagos grazes her knee while playing football. Within a week, new skin has grown over the wound.

   (a)

   Which type of cell division produces the new skin cells that repair the graze?

   [1 mark]

   • AMitosis
   • BMeiosis
   • CFertilisation
   • DBinary fission

   (b)

   How do the new skin cells compare with the original skin cells?

   [1 mark]

   • AThey have half the number of chromosomes
   • BThey are genetically identical to the original cells
   • CThey are genetically different from the original cells
   • DThey have twice as many chromosomes

   (c)

   Explain why the new skin cells have the same DNA as the original skin cells.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A cell biology class in Chennai builds a model of a dividing animal cell. The model parent cell has 4 chromosomes, shown by lengths of coloured wool inside a paper nucleus.

   (a)

   What happens to the DNA before the nucleus divides in mitosis?

   [1 mark]

   • AIt is destroyed
   • BIt is halved
   • CIt is copied
   • DIt is removed from the cell

   (b)

   How many chromosomes does each daughter cell in the model have after mitosis?

   [1 mark]

   • A1
   • B2
   • C8
   • D4

   (c)

   Outline what happens to the nucleus and the cytoplasm after the DNA has been copied.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Researchers in Tokyo study stem cells taken from bone marrow, the soft tissue inside some bones where blood cells are made.

   (a)

   Outline what is meant by a stem cell.

   [3 marks]

   (b)

   Explain how stem cells in bone marrow help to keep the number of red blood cells in the body constant.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A public health agency in Brisbane is running a campaign about skin cancer, which can develop when skin cells are damaged by ultraviolet (UV) radiation in sunlight.

   (a)

   A student wants to test the hypothesis that sunscreen with a higher sun protection factor (SPF) blocks more UV radiation. She has UV-sensitive beads that change colour in UV light, clear plastic bags, and sunscreens with SPF 15, SPF 30 and SPF 50. Plan an investigation. In your answer, state a hypothesis with a scientific reason, identify the variables, and describe a safe method.

   [6 marks]

   (b)

   Discuss and evaluate a government proposal to ban commercial sunbeds. Consider health, social and economic implications, and finish with a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions