Chromosome q arm:Every human chromosome consists of two arms—a short one and a long one—divided by the centromere, which connects the chromosome to the spindle during cell division. According to international standards, the short arm is called the "p arm," and the longer one is the "q arm."Examples of p and q usage:A deletion in the 5p (short arm of chromosome 5) leads to Cri du Chat syndrome, characterized by a cat-like cry. An additional copy of part of 21q (long arm of chromosome 21) results in Down syndrome.Origin of p and q for chromosome arms:The "p" symbol was chosen for the short arm because "p" stands for "petit," which means "small" in French. "Q" was selected for the long arm simply because it follows "p" in the alphabet.
