P is for petite (i.e short arm) and 'q' follow 'p' in the alphabet

P is for petite (i.e short arm) and 'q' follow 'p' in the alphabet

Thank you ros

Totally agree!

P --> "Petite" in french, and next letter is Q, chosen for the big one.....

Just a historical addition here. In one of the early human chromosome nomenclature workshops, London 1958 I believe, Jerome Lejeune, the French discoverer of trisomy 21 fame proposed using "p" and "g" as abbreviations for "petit" and "grand" for the short and long chromosome arms respectively. However, Lejeune was outvoted by the anglosaxon delegates who pointed out the "p"and "q"already existed as well known abbreviations in Hardy-Weinberg statistics as two alternative genetic states and therefore were also appropriate for referring to chromosome arm length differences

Interesting Q&A, but is there verifiable evidence for any of these explanations?

Hello Calvin, A good question from a suspicious independent researcher. I first heard this as an anecdote from my boss Alan Stevenson who got it directly from Lejeune himself in the mid 60s. However, this has also been a discussion point in an urban myths in genetics series, where scepticism was also expressed over the origin of p and q: I have just traced this and my response above was entirely based on memory. See http://thednaexchange.com/2011/05/02/p-q-solved-being-the-true-story-of-how-the-chromosome-got-its-name/ for confirmation.

Oops - further to my responses on the origin of the p and q terminology for chromosome long and short arms respectively, I wish to apologise in my loss of memory in suggesting that the p and q discussion came up at a chromosome nomenclature workshop in London, 1958 when in fact it was Chicago, 1966 - some how, in memory, the decades have become condensed into years. I never attended these early workshops myself and only became personally involved in human chromosome nomenclature affairs from Paris 1972 onwards.

Thank you very much dear Peter for your response and nice information

Hi Zina , one of the stories is that P =Petit (which means small) for short arm and q is the letter that follows P in English alphabet...so its sequentially arranged

Another tricky answer is that P has came from Petit and as far as the long arm is the opposite arm to the short arm ,, Consequently the reverse of p is q !!!

Hope this would be satisfactory

The centre region of Chromosome known as Centromere controls the movement of cell division. On either side are arms that terminate with "Telomers".Short arm is reffered to as "p"&long arm "q".The pattern of light &dark bands seen in the short arm is less when compared to the long arm& this results because of different amounts of A&T versus G&C bases across the Chromosome.

Thanks all respectable scientists,very valuable answers