What is the basis of two types of tests were being done? Why might two types oftests be required for triplet repeat expansions

The two types of tests typically done for triplet repeat expansions are DNA sequencing and repeat-primed PCR.

1. DNA Sequencing: This is a method used to determine the precise order of nucleotides within a DNA molecule. It includes any method or technology that is used to determine the order of the four bases—adenine, guanine, cytosine, and thymine—in a strand of DNA. In the context of testing for triplet repeat expansions, DNA sequencing can be used to identify the exact number of repeats present in the gene of interest.

2. Repeat-Primed PCR: This is a specialized type of polymerase chain reaction (PCR) that is used to amplify DNA with repeat expansions. The method uses a primer that is complementary to the repeat sequence, allowing for the amplification of the repeat expansion. This method can detect even very large repeat expansions, which can be missed by DNA sequencing.

Two types of tests might be required for triplet repeat expansions because each test has its own strengths and limitations. DNA sequencing can provide precise information about the number of repeats, but it may not be able to detect very large expansions. On the other hand, repeat-primed PCR can detect large expansions, but it does not provide precise information about the number of repeats. Therefore, using both tests together can provide a more complete picture of the repeat expansion.