You arrive at a crime scene as a forensics analyst. At the scene you find blood, saliva, and semen of the suspect. You decide to use DNA fingerprinting to match against the suspect

Question

You arrive at a crime scene as a forensics analyst. At the scene you find blood, saliva, and semen of the suspect. You decide to use DNA fingerprinting to match against the suspect

You have matched the samples from the scene to the primary suspect. However, the suspect has an identical twin. You may use DNA fingerprinting to differentiate between the twins with the saliva and semen samples, but not the blood sample. Explain why.

Answer 1

DNA fingerprinting analyzes specific regions of the DNA sequence that contain genetic variations unique to each individual. However, identical twins are formed from a single fertilized egg that splits into two embryos, resulting in two individuals with almost identical DNA sequences. Identical twins share the same DNA profile, including the same genetic variations that are used in DNA fingerprinting analysis. In the case of blood samples, there may be no genetic variation in the region of interest that can be used to differentiate between the twins, as identical twins can have identical blood group and other blood markers. However, saliva and semen samples are more likely to contain different genetic variations due to environmental factors and mutations that occur after fertilization, making it possible to differentiate between the twins using DNA fingerprinting.