Question

During a murder investigation, blood stains from the crime scene, blood of the victim and 3 suspects were collected. DNA fingerprinting was performed for all of them and the autoradiogram thus obtained has been given below.

Which of the suspects is likely to have committed the crime?

• A. Suspect 1
• B. Suspect 2
• C. Suspect 3
• D. Blood stain collected at crime site is of victim

Answer 1

The correct option is B Suspect 2

DNA fingerprinting is a laboratory technique which relies on the repetitive sequences of DNA of a person to determine his/ her unique identity. The end result of a DNA fingerprinting is an autoradiogram which is a piece of X-ray film with dark bands.
Since polymorphism exists in the individuals of a species in a population, the fragments generated on restriction digestion of two individuals are not the same. Hence, the DNA bands of two individuals are not identical except for monozygotic twins.
Upon carefully studying the figure, we can see that all the DNA bands of suspect 2 are matching with the bands of the autoradiogram developed from blood obtained at the crime site. Since all bands of blood stain are matching with suspect 2, he is the most likely to be the criminal.