1. Cystic fibrosis (CF) is an autosomal recessive disorder....

1. Cystic fibrosis (CF) is an autosomal recessive disorder. Normally, both parents must be carriers of the CF gene in order for the child to inherit the disorder. In 1998, Arthur Beaudet of the Baylor College of Medicine saw a very unusual CF patient. Testing revealed the following: 1) the mother was a CF carrier 2) the father had two wild-type alleles 3) both of the patient's chromosomes that contained the CF gene had come from her mother. It was determined that nondisjunction must have occurred in both oogenesis of the mother and spermatogenesis of the father to create the patient's odd combination of alleles. Diagram the 2 nondisjunction events that occurred in meiosis of the father and of the mother. Then show which two gametes fused to produce the CF patient's phenotype. 2. A man has an extra toe on each foot as a result of a dominant trait that he inherited from his mother. His mother's mother and his mother also had the trait. The man falls in love with a ten-toed beauty and their first child, a boy, has a normal number of toes. A. Draw a pedigree for this family and show all genotypes. B. What is the chance that their next child will have 12 toes like it's father?

Transcript

00:01 And not to answer this question, let's talk about, well, chromosomes.

00:05 Question number one says, sisyphibrocy is an autosomal with a disorder.

00:08 Normally both parents must be covered for the scy fibrocybrosis jig in order for the child to inherit a disorder.

00:14 So here you have that, well, a person, so a very unusual sisyphibarosis patient.

00:21 And testing will be the following.

00:22 The mother was a sisyphorosis cover.

00:24 So the mother is going to be like this.

00:25 This is a genotype for the mother.

00:27 The father had two wild terbalil.

00:28 So this is, this was a genomes.

00:29 For the father.

00:31 Okay? and both of the patients ' chromosomes that contained that cystic fibrosy gene had come from her mother.

00:39 So, practically, you found here that they had a child, and this child had, well, had cystic fibrosis, but these two recessive a came from the mother.

00:49 Well, this is true because the father does not have any, any recessive allele or cystic borosal.

00:54 So what happened here? it says it was determined that a non -discence function must have occurred in both or genes.

01:00 Of the mother and also in the sprematogenesis of the father to create the patients or combination of alleles.

01:06 Diagram that two non -disjunction events that occurred in myiosis of the father and of the mother then show which two gametes fused to produce the cystic fibrosis patients phenotype.

01:16 So normally, normally this is what happens.

01:19 Let's suppose this is the woman, okay? during myosis one, you're going to have that in general.

01:25 This is a general perspective.

01:27 This dominant aphan is from here and degrees sensitive aisph here.

01:29 Here then you're just going to copy each of these allele and during myiosis 2 we're going to produce two dollar cells per cell and you're going to produce here a a precessive a in this case.

01:39 Okay, so you're just copy these two all these here and these are going to be in case of the mother, like the possible eggs that she can produce.

01:47 But what happens during a non -disjunct in the mother? well, in case of the mother, what is happening is a non -dischung in myiosis 2.

01:55 Okay, so you're going to have this during myiosis 1, everything is going to be fine.

01:59 You're going to have here a and a and during myiosis too in this case nothing happened this is going to be normal but in this case non -dischension occurred and instead of the of one recessive a moving here and one reclusive a moving here both recessive a are going to move into one set so you're going to have a a like two recessive a at least here and zero here okay so this is what happens in the model now in the father in the father this is going to put the father and practically in the father and the at myosis 1 or myosis 2, here it is not too important, but let's suppose that it happens in myosis 1.

02:38 Okay, so you're going to have here that both a's go here, then both a's are going to go here, and this is a, oh, sorry, this is, or well, yeah, this is a aa, aa, because you're just, we're just copying this to here and here, and here, and here we're going to have a 0, 0, 0, okay? so, this is sperm, sperm, sperm, sperm, and this is in these are eggs.

03:01 So you want to produce a child with that is homocybo -gesessive in order for the child to have cystic fibrosis.

03:08 So what happened here is that this woman selected an egg with these two gaseaseaseasease -a alleles.

03:15 Okay, so you're going to have this ovum or homocyte and the sperm is going to be an empty, an empty sperm that does not have any allele for the cystic fibrosis.

03:29 Okay? so you are going to fuse this and you're going to cause.

03:33 As i go, there is going to be a future baby with 46 chromosomes and this genotype for the cystic fibrosis gene.

03:41 It means this patient is going to have cystic fibrosis where two with sensitive chromosomes came from the model.

03:49 So this is the answer for this question.

03:52 The next question says a man has an extra toe on each foot as a glyphalo adobeinate rate that he inherited from his mother.

03:59 So a genotype for this man is going to be like this.

04:04 Okay, remember that, well, in this case, extra toe is dominant and the recessive is, well, normal food...

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