Galactosaemia is a rare genetic disease in which the build-up of the monosaccharide galactose can result in an enlarged liver, kidney failure and brain damage. Galactose is produced in the body from the digestion of the sugar lactose, found in milk. Galactosaemia is caused by a recessive mutation of the GALT gene. The normal dominant allele codes for an enzyme which converts galactose to glucose. (b) If the phenotypes of parents are known, the probabilities of having a child with galactosaemia, an unaffected child (healthy, not a carrier) or a child who is a carrier can be calculated. Complete Table 7.1 to show the results of these calculations. [Table 7.1]

1. (a)(i)Suggest how a person with galactosaemia can minimise damage to the liver, kidney and brain.[1]
2. (a)(ii)Explain how a mutation in the GALT gene could result in a change in the enzyme responsible for the metabolism of galactose.[4]
3. (b)If the phenotypes of parents are known, the probabilities of having a child with galactosaemia, an unaffected child (healthy, not a carrier) or a child who is a carrier can be calculated. Complete Table 7.1 to show the results of these calculations. parent 1 parent 2 percentage probability of having a percentage probability of having an child with unaffected child galactosaemia unaffected carrier 0 50 carrier carrier unaffected has galactosaemia has carrier 50 0 galactosaemia percentage probability of having a child who is a carrier 50 50[2]
4. (c)Testing for galactosaemia is usually carried out on newborn babies, although it is possible to carry out the test on a foetus. Explain how the presence of galactosaemia in a foetus may be determined.[2]