Final answer:
A researcher studying GC content is examining the percentage of guanine and cytosine bases in a DNA sequence, reflecting base pairing and DNA stability.
Step-by-step explanation:
When looking at the GC content (or G+C content), a researcher is studying the percentage of guanine and cytosine bases in a DNA sequence. This is essential for understanding the base composition of DNA and is used as an indicator of the DNA's stability, among other factors. The DNA molecule is made up of four different nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C). As per Chargaff's rules, discovered by Austrian biochemist Erwin Chargaff, there is a direct equivalence in the amounts of adenine to thymine (A=T) and guanine to cytosine (G=C) within a DNA molecule. This equivalency plays a crucial role in the DNA's double helix structure, where A pairs with T, and G pairs with C.