In the absence of a particular human enzyme the sugar...

In the absence of a particular human enzyme, the sugar galactose is not metabolized and instead accumulates in the body, adversely affecting the development of the nervous system in infant children. This disorder, known as galactosemia, is due to the expression of an allele, g, which is recessive to the allele for normal enzyme production g+. Through an analysis of their family's genetic history, both phenotypically normal members of a couple are identified as heterozygous for the alleles governing this trait. What is the probability that:

Transcript

00:01 To answer this question, let's talk about inheritance.

00:02 It says, in humans, there is a disease called a phenyl ketoneuria, that is pqau, which is caused by a excessive allele.

00:09 So let's suppose that in this case, the homozygous dominant and the heterocygous are going to be for a normal person, while the homozygum recessive is going to be for pqau.

00:20 Now, it says, people with this allele have a defective enzyme and cannot break down the amino acid phenylalanine.

00:26 This disease can result in mental retardation or death.

00:30 Also in humans there is a condition called galactose intolerance or galactosinia, which is also caused by a recessive a little.

00:37 And in this case, you're going to use that g.

00:38 So when you have the homozygous dominant or the heterozygos, you're going to have, you're going to be normal, practically.

00:45 But when you have the homozybolysis, you're going to have galatoemia.

00:52 Garagosimia, okay? now, it says, in both diseases normal dominates over recessive.

01:00 Well, we have already know that.

01:02 If two adults were heterocygoyal for both traits, it means if both are heterocygose for both genes, what are the chances of having a child that is completely normal? so when they give you the specific genotype or phenotype that they want you to get, you can spare making a type -harmia pannide square that takes longer.

01:22 And in this case, you can make two monohalbohabular square crossing this one with this one and this one with this one.

01:28 Okay, so you have the heterocygoyles e with the heterocylus e, you have small -saccharacteroid.

01:34 Heterocygote, heterocyg, homocybozygos, the same for the g, have the heterocyg with the heterocylus g you have homocygous g, homozygos, heterocygous, and homocygose, recessive.

01:48 So, in this case, they are asking you for the chances that they have a child that is completely normal...

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