Question

(a) Phenylketonuria (PKU) is an inherited disorder controlled by a single gene.
People with PKU have to limit how much protein they eat.
The allele for PKU is recessive (d).
Fig. 4.1 is a pedigree diagram showing the inheritance of PKU in one family.

(i) Use Fig. 4.1 to state the number of people:
that are homozygous recessive for PKU …………………..
with XX chromosomes. …………………..
(ii) The two people in generation 1 in Fig. 4.1 have the same genotype.
State this genotype.
(iii) State the percentage likelihood of an offspring having PKU if both parents have
heterozygous genotypes.

(b) State the names of two diseases that are associated with protein-energy malnutrition.
1 ………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
(c) Table 4.1 shows some large nutrient molecules.
Complete Table 4.1 to name the smaller molecules from which they are made.

(d) State the name of the enzyme that breaks down protein.