When a DNA analysis reveals a closely guarded family secret… Premium

Government lab in Hyderabad, CDFD provides DNA services to police, judiciary, and hospitals, revealing levirate practices in families.

The Centre for DNA Fingerprinting and Diagnostics (CDFD) is a government laboratory in Hyderabad. It provides DNA-based investigative services to the police, the judiciary, and to hospitals that offer organ transplant procedures. Recently, the CDFD handled the case of a family in which the father offered to donate an organ to his ailing son. CDFD technicians generated DNA profiles of the donor, the patient, and also the patient’s mother.

While the DNA profiles of the mother and the son were consistent with their claimed mother-son relationship, those of the father and his son were not. The DNA showed that the woman’s husband was not the actual father of the patient but a close paternal relative, possibly a brother of the actual father. These findings didn’t preclude the organ transplant procedure but by revealing the practice of levirate they created a potentially awkward situation for the family.

Levirate is the custom in some families in which a woman who is widowed or one whose husband is mentally or physically incapacitated has children fathered by her husband’s brother. Understandably, the family would prefer to keep such knowledge private. The report from the CDFD was meant to tell doctors they could proceed with the transplant operation because the donor and the recipient belonged to the same family. But by explicitly revealing the woman’s husband was not her son’s father, it created the risk of an unwanted breach of the family’s privacy.

Every cell in our body has a nucleus that contains two copies of each of the 23 chromosomes, numbered 1 to 23. This 1-23 lump is our genome. One chromosome of each pair is inherited via the mother’s egg and the other via the father’s sperm.

When we make our own reproductive cells — eggs or sperm — each egg or sperm receives only one chromosome from a pair, i.e. one genome set. When a sperm cell and an egg fuse, they create a cell with two genome sets. This cell, called the zygote, divides to produce all the other cells of the baby.

Every chromosome contains a single DNA molecule that runs from end to end. A DNA molecule has two strands. Each strand is a long, linear sequence of four chemicals: adenine (A), cytosine (C), guanine (G), and thymidine (T). The As on one strand form bonds with the Ts on the other, while Gs bond with the Cs. The As, Cs, Gs, and Ts on one strand are called the DNA’s bases and the A-T and G-C combinations are the DNA’s base-pairs.

The largest chromosome in humans, chromosome 1, has more than 240 million base-pairs; the shortest, chromosome 21, has more than 40 million. The 23 chromosomes together have 3.2 billion base-pairs.