Kids of related couples prone to acute congenital diseases

CDFD develops technique for prenatal diagnosis of single-gene disorders

​Hyderabad: Marriages between first cousins, maternal uncle and niece, blood-related or biologically related couples can result in serious congenital disorders in their children.

Even progeny of married couples who have the same ancestral lineage could be prone to what is termed as single-gene disorders.

In India, this practice known as consanguineous marriages, is widely prevalent, specifically among those couples who lack awareness of the consequences on their off-spring or skeptical about such an eventuality.

According to scientists, children of such parents can be susceptible to genetically inherited disorders like congenital malformations, Thalassemia, Sickle Cell anemia, and various amino acid disorders.

Thalassemia and Sickle Cell anemia are inherited blood disorders in the form of haemoglobin abnormalities. Till date there is no cure for these disorders.

In a breakthrough that facilitates diagnosis of single gene disorders at the early stage itself, scientists at the Hyderabad-based Centre for DNA Fingerprinting and Diagnostics (CDFD) have developed the methodology for detection of sequence in the gene which causes these conditions.

The unraveling of the DNA sequence is of crucial significance since it can help detect the disorder in the patient as well as during the very early stages or the prenatal stage.

“The identification of the DNA sequence has enabled us to develop a diagnostic technology to detect these disorders at the prenatal stage,” Dr Ashwin Dalal, Head, Diagnostics Division, CDFD, told The Hans India.

With this diagnostic sequencing process, blood related or closely-related parents can now know in advance whether their yet to-be-born child is likely to have inherited the defective gene.

According to Dr.Ashwin Dalal, single gene disorders occur if the child gets defective copies on both the genes.

“Among blood related married couples, both parents may be carrying one normal gene and one defective gene. There are two possibilities which can occur in the child.

One possibility is that the child may get copies of normal genes from both parents or one normal gene and one defective gene from the parents.

For instance, the baby may get a normal gene from the mother and the defective gene from the father or vice-versa. In this situation the child will be normal.

Single gene disorder occurs when the child receives only the defective genes from both the parents,” he explained.

In other words, if the faulty genes from both the parents are passed on to the child then the combination manifests in the form of single-gene disorders.

Couples from a common ancestral lineage might have been carrying both normal and the recessive or the mutant of the defective genes, but the disorder may not have had expressed in the form of single gene disorder in either of them because of the normal gene dominating the faulty gene.

“We employ whole exome sequencing, to identify mutations in such affected families. Samples are drawn from the child of such parents and we apply exome sequencing which is a precision technique used at the CDFD to pinpoint the cause of single gene disorder.

This method enables the parents to go for prenatal diagnosis and then take a decision on whether to abort the child if the foetus is affected, since abortion is permitted in India within a period of 20 weeks since conception,” he said.

By: Satyapal Menon