Question

Which of the examples of genetic testing below are prognostic tests? Which are diagnostic?

Individual sequencing (personal genomics) identifies a mutation associated with Alzheimer's disease.

Accepted Answer

Hi, everyone. Welcome back. Let's look at our next problem here. If a person inherits a genetic mutation that causes a certain disease, then the patient can usually manifest genetic diseases like sickle cell anemia, cystic fibrosis and some cases of early onset Alzheimer's disease. The three single gene mutations associated with early onset Alzheimer's disease are and then our answer choices present us with lists of different gene mutations. So early onset Alzheimer's disease is quite rare. It accounts for less than 10% of the total number of cases of Alzheimer's disease, but it has a very strong genetic linkage and it involves Alzheimer's disease that has this early onset between age 30 and 60 compared to the more usual later onset of Alzheimer's disease. Uh and is inherited at least the gene mutations that we know of are inherited in autism als dominant pattern. So seeing very strongly um running in families. So I'm just gonna list here briefly, the three G mutations we know that are associated with early onset Alzheimer's disease. So mutations to amyloid precursor protein or A P P uh pre seasonal in one PSC N one or prison Ellen to PSC N two. So, mutations in the genes for these proteins are known to cause early onset Alzheimer's disease. Um They're, the causation is because amyloid precursor protein is cleaved and prison all in one and personnel and to our part of the enzymatic enzymatic complex that does that cleaning. One of the products of that cleavage is a peptide fragment called amyloid beta peptide. And if this product builds up in large amounts in the brain, it sticks together in clumps called plaques. And those plaques seem to cause the damage that causes the characteristic symptoms of Alzheimer's disease. So, these are all three involved in the production of that Amyloid beta peptide and then excess amount. So when something goes wrong with this process, causing excess, build up of that peptide um that forms the plaques in the brain that are characteristic of Alzheimer's disease and are thought to cause the damage that leads to the dementia associated with it. So, with that in mind, let's look at our answer choices to find the correct description of the three single gene mutations associated with this. So we see choice. A says Amyloid precursor protein on chromosome 21 prison Ellen one on chromosome 14 and personal in two on chromosome one. And those are three mutations that we know of. So we're gonna go and select choice. A is our answer since we don't have anything like. And all of the above, it's interesting to note that these mutations occur on three different chromosomes. So even though they're all involved in the same process, that genes are present on different chromosomes. Choice B says a polyp A protein E A P O E gene on chromosome 19 and then A PP on chromosome 21 P SCN one on chromosome 14. Well, A that, that A P O E JEAN um is involved in Alzheimer's disease, but in the late onset form particular mutations in that gene, a particular value of that gene is associated with a slightly increased risk of developing the more normal, late on or more common late onset Alzheimer's disease. Uh It's not a strong link as we know, these three gene mutations uh seem to cause early onset Alzheimer's disease. Whereas that A P O E JEAN just causes a slightly increased risk. But that's my choice B is not correct but increased risk. Then choice C we C also has a P O E gene on chromosome 19 as one of the list. So that's why it's not the answer. And then choice D also involves a list of the A P O E JEAN which rules it out as well. So again, the three B C and D all involved this gene that causes an increased risk of the regular late onset Alzheimer's disease. Uh the single gene mutations assisted with early Alzheimer's disease. Our choice, a amyloid precursor protein on chromosome 21 personal and one on chromosome 14 and personal. In two on chromosome one. See you in the next video.

Which of the examples of genetic testing below are prognostic tests? Which are diagnostic?Individual sequencing (personal genomics) identifies a mutation associated with Alzheimer's disease.

Watch next

Which of the examples of genetic testing below are prognostic tests? Which are diagnostic?

Individual sequencing (personal genomics) identifies a mutation associated with Alzheimer's disease.