Inheritance

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Question 7
Medium

Phenylketonuria (PKU) is an inherited metabolic disorder.

It is caused by a gene mutation that produces a recessive allele, resulting in a non-functional enzyme, phenylalanine hydroxylase.

a.

Explain the meaning of these genetic terms:

  • Homozygous
  • Phenotype
[2]
b.

A parent who is heterozygous for PKU and a parent who has PKU are expecting a child. Draw a genetic diagram to calculate the probability that the child will have the condition. Use PPP for the normal allele and ppp for the allele for PKU.

[3]
c.

Individuals with untreated PKU must strictly limit their intake of protein-rich foods, but can safely consume lipids and simple carbohydrates. Explain why.

[2]
d.

Explain why stem cells programmed to differentiate into liver cells (hepatocytes) could be used as a treatment for PKU.

[2]
e.

Why is it an advantage to use stem cells harvested from the patient (e.g., induced pluripotent stem cells) rather than from a donor?

[1]

Inheritance Questions

  1. GCSE
  2. /Biology
  3. /Inheritance