Question 10
HThe Figure shows a Siamese cat.
Figure
The colour of the fur is controlled by a gene that codes for an enzyme. The enzyme makes a dark pigment in the fur.
In Siamese cats, the allele for this enzyme codes for an enzyme that only works at temperatures below 33 ∘C33\ ^{\circ}\text{C}33 ∘C. Above this temperature the enzyme is denatured.
a.[3]
Explain why Siamese cats have dark fur on their ears, face, paws and tail but pale fur on their body.
b.[2]
A vet shaved a patch of fur from the back of a Siamese cat. An ice pack was kept on the shaved patch while the fur grew back.
Predict the colour of the fur that grew back. Explain your answer.
c.[2]
Explain why the fur colour of Siamese cats is an example of both genetic and environmental variation.
d.[1]
Siamese kittens have completely pale fur when they are born.
Suggest why.
3.4 Variation and the Human Genome Project Questions
40 exam-style questions on Edexcel GCSE Biology 3.4 Variation and the Human Genome Project, covering 3.4.1 Causes of variation, 3.4.2 Outcomes of the Human Genome Project, 3.4.3 Genetic variation within a population, and 3.4.4 Effects of genetic mutations on phenotype. Each one has a worked solution and a mark scheme showing where the marks go.