Galactosemia is a rare disorder caused by the inability to metabolize galactose, a component found in mammalian milk. Galatosemia can be partially managed by eliminating dietary intake of lactose and galactose. Amanda is healthy, but her sister has galactosemia. Brice's family is also affected by the condition. His aunt (his father's sister) has galactosemia. No one else in either family has the condition. Amanda and Brice are planning a family and seek genetic counseling. What is the probability that their first child will have galactosemia?

Classic galactosemia, which can result in life-threatening complications including feeding problems, failure to thrive, hepatocellular damage, bleeding, and E. coli sepsis in untreated infants. If a lactose-restricted diet is provided during the first ten days of life, the neonatal signs usually quickly resolve and the complications of liver failure, sepsis, and neonatal death are prevented; however, despite adequate treatment from an early age, children with classic galactosemia remain at increased risk for developmental delays, speech problems (termed childhood apraxia of speech and dysarthria), and abnormalities of motor function. Almost all females with classic galactosemia manifest premature ovarian insufficiency (POI).

Explanation:

Genetic counseling.

Classic galactosemia and clinical variant galactosemia are inherited in an autosomal recessive manner. Couples who have had one affected child have a 25% chance of having an affected child in each subsequent pregnancy. Molecular genetic carrier testing for at-risk sibs and prenatal diagnosis for pregnancies at increased risk are an option if the GALT pathogenic variants in the family are known. If the GALT pathogenic variants in a family are not known, prenatal testing can rely on assay of GALT enzyme activity in cultured amniotic fluid cells.

0% chances of galactosemia if either Amanda or Brice are

[GG, Gg] or [Gg, GG] or [GG, GG]

25% chances of galactosemia if both Amanda and Brice are Gg

Explanation:

there can be cases in which either Amanda or Brice can be heterozygous or Homozygous. for example G will represent dominant trait that the person is galactosemia negative and g will represent recessive trait that the person is galactosemia positive. Amanda could be Gg or GG, similarly Brice could be Gg or GG.

if Amanda and Brice both are GG then the baby is at 0% risk.

if either Amanda or Brice is Gg then the baby is at 0% risk.

if both are Gg then the baby is at 25% risk.