Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.
The low-methionine diet must be maintained throughout life to manage homocystinuria. Why do you think this is the case?

Question

Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.
The low-methionine diet must be maintained throughout life to manage homocystinuria. Why do you think this is the case?

The low-methionine diet must be maintained throughout life to manage homocystinuria. Why do you think this is the case?

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. Homocysteine area is caused by a mutation that blocks the degradation of the amino acid blake. The answer options are a arginine B Y scene. See matthias nine and D histamine. Now, what is homocysteine Arria? Well, we know from the question that it's caused by a mutation, meaning that it is a genetic disorder and in fact, it's an auto zonal recessive genetic disorder. Now, what amino acid has impaired degradation and causes it recall that the amino acid meth iodine is a precursor to the molecule called homocysteine on the screen. I've put a very simplified image of the Matthiasson in homocysteine cycle. The MMA thiamine which is taken in through our diet is converted into homocysteine, homocysteine then is converted back to MMA thiamine or goes through a pathway to become assisting, Impaired degradation of Matthias nine means homocysteine is not able to go through the pathway to become assisting. What this means is, you therefore get a build up in that homocysteine molecule and that causes the homocysteine urea. Therefore, the correct answer is option C. Matthias 19. Alright, everyone, I hope you found this helpful and I'll see you soon for the next practice problem.

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Key Concepts

Autosomal Recessive Inheritance

Methionine Metabolism and Enzyme Deficiency

Dietary Management of Metabolic Disorders