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Date May 2022 Marks available 1 Reference code 22M.2.SL.TZ2.2
Level Standard level Paper Paper 2 Time zone Time zone 2
Command term Calculate Question number 2 Adapted from N/A

Question

An oval-shaped stem cell cluster is shown in the micrograph.

[Source: Sontag, S., Förster, M., Seré, K. and Zenke, M., 2017. [online] Available at: https://bio-protocol.org/e2419 [Accessed
6 December 2019]. Source adapted.]

State the main characteristic of stem cells.

[1]
a.

Calculate the maximum diameter of the stem cell cluster on the micrograph, showing your working and giving the units.

 

 

 

..........

[1]
b.

State one therapeutic role of stem cells.

[1]
c.

Discuss how the use of stem cells to treat hereditary diseases could affect the person who received the treatment and their progeny.

[2]
d.

Markscheme

undifferentiated/pluripotent/ability to divide/differentiate into any types of cells/differentiate along different pathways;

a.
  1. correct formula: 1.1cm = 500 μm, 2.7cm = length, 2.7×5001.1=Xμm;
  2. correct answer with unit: 1227μm;

Allow answer in range of 1150 μm to 1350 μm.

b.

treatment of Stargardt’s disease/leukemia/diabetes/heart disease/Parkinson’s disease;

Any other verifiable condition.

c.
  1. could improve quality/length of life of the treated person;
  2. disease could still be passed on to progeny if defective gene/allele in gametes is not replaced/changed;
d.

Examiners report

In a. most were able to say the stem cells were undifferentiated. Many put ‘unspecialised’ instead, which was not credited. There were several, justified G2 comments about the size of the micrograph, which made it difficult to measure the diameter accurately. However, this was generally very poorly answered, with over half failing to get the mark for either the correct answer or the correct calculation. In 1d the better candidates stated that the person could now live a normal life, but as it was not in the genome the progeny could still be affected. The word ‘progeny’ was commented on by several teachers, who pointed out that ‘children’, or ‘offspring’ would have been clearer for those working in an additional language.

a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Core » Topic 1: Cell biology » 1.1 Introduction to cells
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