DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ2.2

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Date May 2022 Marks available [Maximum mark: 5] Reference code 22M.2.SL.TZ2.2
Level SL Paper 2 Time zone TZ2
Command term Calculate, Discuss, State Question number 2 Adapted from N/A
2.
[Maximum mark: 5]
22M.2.SL.TZ2.2

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.]

(a)

State the main characteristic of stem cells.

[1]

Markscheme

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

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.

(b)

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

 

 

 

..........

[1]

Markscheme
  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.

(c)

State one therapeutic role of stem cells.

[1]

Markscheme

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

Any other verifiable condition.

(d)

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

[2]

Markscheme
  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;

Syllabus sections