DP Biology (first assessment 2025)

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Question 20N.2.SL.TZ0.b

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.2.SL.TZ0.b
Level SL Paper 2 Time zone TZ0
Command term Determine Question number b Adapted from N/A
b.
[Maximum mark: 2]
20N.2.SL.TZ0.b

Using a Punnett square, determine how a smooth-haired puppy could be produced in the offspring.

[2]

Markscheme

WK Wk wK and wk for male gamete genotypes and wk for female;

wwKk shown in Punnett square and identified as smooth;

Examiners report

There were some complaints from teachers that epistasis is not included in the program. It was not expected that candidates would have studied ratios derived from interaction between genes and instead it was intended that they work out the pattern of inheritance themselves from the information provided. About a third of candidates successfully did this. The Punnett squares drawn up by other candidates often revealed fundamental misunderstandings of dihybrid inheritance.

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