MODEL RELEASED. DNA test for AIDS. Researcher exa- mines the results of a test for HIV virus (the cause of AIDS) on a DNA (Deoxyribonucleic Acid) gel. Bright pink bands on the DNA gel represent specific sizes of DNA fragments. This test is known as PCR (Polymerase Chain Reaction), where specific fragments of DNA can be amplified millions of times. Here, the DNA fragments amplif- ied come from the HIV virus. Small strands of DNA specific for the HIV virus (known as primers) are added to a suspect blood sample. PCR is performed on the sample and specific sized fragments of DNA seen on a gel confirm the diagnosis of HIV.