Which banding technique would be the first choice if a subtle chromosomal rearrangement is suspected?

G-banding is the preferred technique when there is a suspicion of subtle chromosomal rearrangements. This method involves staining chromosomes with Giemsa dye after the cells have undergone a process of pretreatment and trypsinization. G-banding allows for a clear visualization of the banding patterns of chromosomes, showcasing light and dark bands that highlight structural features and possible alterations.

The resolution provided by G-banding is particularly valuable in detecting smaller chromosomal rearrangements such as inversions, deficiencies, or translocations, which might not be evident with less detailed techniques. Since each chromosome has a unique banding pattern, G-banding enhances the identification of specific chromosome regions that may be involved in genetic abnormalities. The overall distinct pattern it creates makes it easier to pinpoint subtle changes that might have clinical significance.

Other methods like NOR banding primarily focus on detecting nucleolar organizer regions, while C-banding gives insight into heterochromatin but may not reveal fine structural alterations. Q-banding, though useful for observing certain chromosome features, does not provide the same level of detail in banding patterns as G-banding does. Thus, for investigating subtle rearrangements, G-banding stands out as the most effective technique.