Question

In humans, the presence of a fissure in the iris is regulated by a recessive gene tied to sex. From a couple between two normal people a daughter was born with the mentioned character. The husband files for divorce on the grounds of his wife's infidelity. Explain the mode of inheritance of character and the conditions under which the lawyer of the husband can use the birth of the affected daughter as proof of infidelity.

Answer 1

Coloboma iridis(a fissure in the iris of the eye ), is an eye abnormality that occur before birth. It is missing pieces of tissues in structure that form the eye, that may present in one of several part in the eye.

1. Fissure in the iris is primarily genetic in origin(because of not proper working of gene, when the eye was forming).
2. It can also happen because of specific genetic syndrome.
3. It can also occure, if the babies exposed to alcohol during pregnancy.
4. This abnormality can happen to a person in a family where no one else is affected.

The reason for this abnormality can be understood by knowing how the eye forms inthe developing baby.

1. Eye starts as stalks coming out of the brain. The tip of each stalk will become the eye. Then the closure starts roughly in the middle of the developing eye. This process is finished in the seventh week of pregnancy. In some case the closure does not happen, this result in fissure in the iris.

Fissure in the iris can also be inherited. It can follow all possible patterns of single gene inheritance, like autosomal dominant, autosomal recessive and X-linked.

1. In one family the disorder will follow only one pattern. In case of an autosomal dominant pattern, a person with coloboma would have one in two chance of passing it to the his or her offspring. It is not possible to give an exact number.
2. So this abnormality can be caused not only by inheritance, there are many other reasons, already mentioned above.