Question

Trace amounts of dioxin were present in Agent Orange, a defoliant sprayed on vegetation during the Vietnam War. Animal tests suggest that dioxin can cause birth defects, cancer, liver and thymus damage, and immune system suppression, sometimes leading to death. But the animal tests are equivocal; a hamster is not affected by a dose that can kill a guinea pig. Dioxin acts like a steroid hormone, entering a cell and binding to a cytoplasmic receptor that then binds the cell’s DNA.

1. Discuss how this mechanism might help explain the variety of dioxin’s effects on different body systems and in different animals.
2. Discuss how you might determine whether a type of type of illness is related to dioxin exposure. Next, discuss how you might determine whether a particular individual became ill as a result of exposure to dioxin. Which would be more difficult to demonstrate?Why?

Short answer

(a) In some animals, dioxin can interfere with the transcription process on binding with DNA. At the same time, it can act as a carcinogen in other animals.

Thus, the dioxin activity within the cell may differ in a different body and animal system.

(b) DNA microarray techniques are used to study the effect of dioxin in a person with ill health.

The second study needs to be carried out by inducing the dioxin toxicity in the normal person.

The second study is more difficult to demonstrate because it is unethical to induce toxicity in a healthy person.

Step-by-step solution

Description of dioxin

The organic pollutant present in the environment that cannot be degraded is known as dioxin. It is toxic. It can cause several types of diseases in the animal as well as human system.

Dioxin accumulates in the human body via the food chain. An overdose of dioxin can cause failure in the detoxification mechanism of the liver and cause diseases.

Explanation for part “(a)”

Dioxin is a substance that shows activity similar to hormones. It interacts with the cytoplasmic receptor present in the cell. It interacts with the cell's DNA and interferes with the transcription process.

It can also induce mutation and can cause cancer. However, the dioxin component cannot react with the cytoplasmic receptor to cause toxicity in some organisms.

For example, the cytoplasmic receptor of the hamster is not compatible with the dioxin component. So, the hamster is not affected by the dioxin dose. However, a guinea pig can be killed due to the dosage of dioxin.

Explanation for part “(b)”

In the first demonstration, a person suffering from ill-health is selected to check the effect of dioxin exposure. The DNA microarray techniques are used to find out the impact of dioxin in the genes.

In this test, the gene expression of the ill person is determined, and it is compared with the gene expression of the normal person.

The second demonstration is carried out to induce the dioxin dose to the healthy individual. The illness is generated due to over-accumulation of the dioxin. The overdosage of dioxin can cause diseases in healthy individuals.

The second demonstration is challenging because it is unethical to use healthy individuals to induce the disease and study the effect of dioxin.