q arm of a chromosome

q arm of a chromosome: The long arm of a chromosome. All human chromosomes have 2 arms - the p (short) arm and the q (long) arm - that are separated from each other only by a primary constriction, the centromere, the point at which the chromosome is attached to the spindle during cell division. The symbol "p" stands for "petit", small in French, while "q" was chosen merely because it was the next letter in the alphabet.