The science behind the paternity test

G V Joshi

The recent court case about establishing the paternity and maternity of Delhi based advocate Rohit Shekhar is well-known to one and all.

From the finding of the DNA test carried out at the Government run laboratory at Hyderabad, the court declared that Rohit Shekhar was the biological son of senior Congress leader ND Tiwari and Ms Ujjwala Sharma.

The blood samples of the youth Rohit Shekhar and his mother Ujjwala Sharma were collected in the Delhi High Court on May 26 2012 while Tiwari gave his sample in Dehradun after three days, as per the Supreme Court order.

In law, paternity is the legal acknowledgment of the parental relationship between a man and a child usually based on several factors. At common law, a child born to the wife during a marriage is the husband’s child under the ”presumption of legitimacy”, and the husband is assigned complete rights, duties and obligations as to the child.

The procedure of determining a child’s biological father, or possibly of excluding other candidates, is called a paternity test.

How was  it done earlier? Before the advent of DNA testing, a paternity test usually excluded candidates rather than identifying them. Blood samples were drawn from the child and suspected fathers. Through simple blood typing, a potential father could be eliminated quickly.

If the child’s blood was B type component the potential father  was strictly A, the paternity test would exclude him as a parent. This did not mean, however, that another candidate with blood type B was necessarily the father. A better paternity test was needed to include specific markers for a child’s biologcal parent.

How is it done today? As of today, it is done by what is called as Genetic fingerprinting. It is same as DNA fingerprinting, DNA testing, DNA typing, DNA profiling, DNA analysis, DNA paternity testing and the like.

A DNA paternity test compares a child’s DNA profile with those of his/her mother and alleged father. The profiles are used to distinguish between individuals of the same species using only samples of their DNA.

What is DNA ? DNA is short for Deoxyribonucleic acid. It is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms. It is an important component of body cells. It is an  enormous, complex molecule found in the nuclei of all cells in the body.

DNA  carries the genetic code and is responsible for passing information on from one generation to another. The DNA segments carrying this genetic information are called genes.

DNA was first isolated, analyzed and recognized as a unique macromolecule by Friedrich Miescher in 1869, an eminent physiological chemist from Switzerland, who isolated it from the discarded surgical bandages containing pus. He called it ‘nuclein’, since it was located in the nucelus of the cells.

In 1928, Frederick Griffith performed experiments to prove that DNA carried genetic information. Thereafter, Oswald Avery along with his co-workers identified DNA as the transforming principle in the year 1943. The role of DNA in heredity was confirmed in 1952, when Alfred Hershey and Martha Chase showed that DNA is the genetic material.

In the year 1953, two biologists James Watson and Franklin Crick, with the  help of Rosalind Franklin conducted a detailed study and discovered that human DNA consisted of two strands interlocked with each other and formed a double helix mode. This model was named as the Watson Crick model of DNA in honor of these two scientists.

James Watson and Franklin Crick were awarded Nobel Prize in 1962 for this fundamental research. Rosalind Franklin had passed away in 1958.

Main tasks carried out by deoxyribonucleic acid (DNA) are the transfer of hereditary information from one generation to the next. Determining the paternity of a child is possible with the help of DNA paternity testing procedure. It  helps in identifying the parents and thereby, solving legal cases.

The process of Genetic Fingerprinting was invented by Sir Alec Jeffreys at the University of Leicester and was announced in 1985.

The DNA Paternity testing is based on the premise that an individual inherits one-half of their DNA from each biological   parent. This involves the analysis of samples provided by the mother, child and alleged father. By testing the mother, one can determine which genetic markers are inherited from the mother and hence the remaining genetic markers then must originate from the father.

There is no age or time limit with DNA analysis. Since only a small sample like a drop of blood or swab is required, testing can be conducted with samples from infants, including newborns right up to any age. Testing can also be performed on individuals sampled weeks, months, years, or even, miles apart. A biological sample that is properly taken and stored is very stable.

The DNA test looks at least 16 specific locations on the DNA to see if those locations have corresponding matches in the mother’s and father’s DNA. DNA testing is the most accurate method (nearly 100 per cent) available for determining paternity.

Today, DNA fingerprinting has become an indelible part of society, helping to  prove innocence or guilt in criminal cases, as well as clarifying paternity.

The most prominent use of the DNA fingerprinting is the personal identification. DNA finger printing comprehensively and accurately recognizes the DNA of a person than any other technique available.

Personal identification has been a boon in many fields, namely crime investigation and forensics.

Researchers had found 28 cases in which DNA test results obtained subsequent to trial proved that, the convicted persons could not have committed the crimes for which they were arrested and punished.

The DNA finger printing was used to identify the remains of the Tsar Nicholas Romanov and his family, which, was murdered by Bolsheviks following the Russian revolution of 1917. It was prominently used for identifying the remains of the 9/11 in the US. The technique was instrumental in identifying several thousand remains of the victims.

DNA testing can be used to learn a number of things about a person  including his susceptibility to a range of diseases. DNA fingerprinting can also be used for Kinship testing determining whether individuals are related. This is the first time in India that the result of a DNA paternity test has been made public in a court, after a ward moved a petition to establish his parentage.

Till now, it was more common for partners and spouses to file suits to establish  the paternity of their children. (PTI)


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