And the build up of the galactose can lead to many different problems as we'll see in just a moment. Now, classic galactosemia is an autosomal recessive disease. And what that means is, so let's suppose we have some chromosomal pairs, that individual, what that basically means is these are two genes, two alleles for the same type of enzyme, for some specific type of enzyme. And in this particular case, this gene is for the enzyme we call galactose one phosphate urigal transphrase. And we'll see what it does in just a moment. And in individuals who have classic galactosemia, this gene or both of these genes are actually mutated.