2020HSCShort answer

Q26 (a)

2 marks

Question

One of the genes involved in determining the colour of a species of fish has two alleles: yellow and orange. The diagram shows a pedigree chart for the inheritance of colour in the fish.
Use the pedigree chart to explain why the yellow allele is recessive.

Try the question before revealing the answer.

Solution

Criteria	Marks
• Uses the pedigree chart to explain that the yellow allele is recessive	2
• Provides some relevant information	1

Sample answer:

The inheritance of yellow colour is recessive since both parents are orange but have yellow offspring. The yellow allele must be present in both parents but it is not expressed.

Supplied marking guidance · human reviewed

Compare this with your working, not only your final sentence.

Syllabus alignment

Module 5 · Heredity

Genetic VariationInterpret inheritance patterns, pedigrees and Punnett squares to model genotype combinations.

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