Final answer:
Forensic scientists use DNA to identify individuals because each person's DNA is unique due to variability in the sequence, aside from identical twins. DNA analysis, which involves PCR amplification of STR regions and electrophoresis, provides a unique profile to match individuals with crime scene samples or profiles in databases.
Step-by-step explanation:
Forensic scientists can use DNA to identify an individual because each person's DNA is unique (with the exception of identical twins). This uniqueness is due to the variability in DNA sequences found within the human genome. The human haploid genome contains 3 billion base pairs, with each cell having 23 pairs of chromosomes made up of thousands of genes that determine one's genotype and phenotype. DNA can be obtained from various sources such as hair, blood, or saliva and analyzed for matches in a forensic context.
Moreover, forensic DNA analysis primarily involves the amplification and sequencing of specific regions called short tandem repeats (STRs). These portions of the DNA have high variability among individuals, making them ideal for identity verification. The forensic scientists compare DNA samples to profiles within databases to find a match. However, it's important to note that DNA databases do not contain the DNA of every person—only those who have been collected for legal or scientific purposes.
For successful analysis, forensic scientists employ techniques such as polymerase chain reaction (PCR), which amplifies the DNA, and electrophoresis, which helps in determining the length of amplified fragments. The collected data provides a DNA profile that can be used to identify individuals in criminal investigations and other legal matters.