Question

People are unable to break down trimethyl-amine, a compound in the diet, resulting in a fish-like odor in sweat, urine and breath.

1. Name the trait that causes these symptoms.

2. If this is a heritable trait, what is the mode of inheritance?

What is the type of mutation cause this syndrome, explain the change?

Answer 1

Ques.1: Name the trait that causes these symptoms.

Ans.1:

The trait that causes these symptoms is called as Trimethylaminuria,a genetic disease commonly called as 'Fish odor syndrome',caused by the mutation in the FMO3 gene.When certain types of food like eggs,liver,fish etc are digested,a nitrogen containing compound such as trimethylamine is also produced in the intestine.This compound has a rotten fish odor.Since,in the person affected with this disorder the break down of trimethylamine does not takes place, it starts to accumulate in the body and eventually released in the sweat,urine,breath and reproductive fluids.This results in a characteristic fish-like odor in the sweat,urine and breath of person affected with this trait. There is no cure for this disorder and symptomatic treatments are usually done to reduce the amount of trimethylamine secreted on the skin by the help of laxatives,antibiotics,riboflavin supplements etc. Treatment also includes certain dietary restrictions.

Ques.2: If this is a heritable trait, what is the mode of inheritance?What is the type of mutation cause this syndrome, explain the change?

Ans.2:

Trimethylaminuria which is a genetic disorder that is inherited in an autosomal recessive manner,that is by the alteration of two copies of the gene in each cell. For a person with this autosomal recessive disorder,both the parents carries one copy of the altered gene and may exhibit mild symptoms of trimethylaminuria which can be temporary.

Trimethylaminuria is a genetic disease caused by the mutation in the FMO3 gene.FMO3 is a gene that is responsible for making an enzyme that breaks down the nitrogen containing dietary compounds,including trimethylamine.In a person with Normal FMO3 gene, the enzyme produced will convert the trimethylamine into another molecule that is odorless.

Flavin-containing monooxygenase 3 gene (FMO3) gene has the ability to make an enzyme that catalyzes the N-oxygenation of the fishy smelling trimethylamine.A mutation in the long arm of chromosome 1 of this FMO3 gene,decreases it ability to catalyze the break down of trimethylamine by preventing the enzyme from functioning properly and as a result trimethylamine begins to build up in the body,and eventually released in sweat,urine and breath.