q in population genetics: The frequency of the less common of two different alternative (allelic) versions of a gene. (The frequency of the more common allele is p).

Q bands: The alternating bright and dull fluorescent bands seen on chromosomes under ultraviolet light after the chromosomes are stained with quinacrine. The Q stands for Quinacrine, an agent used as an antimalarial agent and, in the laboratory, as a fluorescent dye.

q.d.: Seen on a prescription, q.d. (or qd) means one a day (from the Latin quaque die).

Q-fever: An acute (abrupt-onset), self-limited febrile illness first reported in 1935 in Queensland, Australia. The Q is said not to be for Queensland, but for Query since the cause of the disease was long a query (question mark). It is now known to be due to Coxiella burnetti, a rickettsia (a peculiar group of bacteria). Aside from sudden onset of fever, there is headache, malaise, and pneumonia (interstitial pneumonitis) but no rash.

q.i.d.: Seen on a prescription, q.i.d. (or qid) means 4 times a day (from the Latin quater in die).

q.h.: Abbreviation for "every hour." On a prescription or doctor's hospital orders, q.h. means every hour. Also written qh (without the periods). From the Latin quaque die.

q.n.s.: On a lab report, q.n.s. (or qns or QNS) means Quantity Not Sufficient. Not enough blood, urine or whatever to do the test.

QRS complex: The deflections in an electrocardiographic (ECG or EKG) tracing that represent the ventricular activity of the heart.

Quackery: Deliberate misrepresentation of the ability of a substance or device for the prevention or treatment of disease. We may think that the day of patent medicines is gone but look around you and you will see them still. They appeal to our desire to believe that every disease is curable or at least treatable. Quackery also applies to persons who pretend to be able to diagnose or heal people but are unqualified and incompetant.

Quadrant: A quarter. For example, the liver is in the right upper quadrant of the abdomen.

Quadriceps: Any four-headed muscle but usually refers to the quadriceps muscle of the thigh, the large muscle that comes down the femur (the bone of the upper leg), over the patella (the kneecap) and anchors into the top of the tibia (the big bone in the lower leg). The function of the quadriceps is to straighten out (extend) the leg. For those who are into Latin, this muscle's name is musculus quadriceps femoris. For those who prefer nicknames, it is the quad.

Quadriparesis: Weakness of all four limbs, both arms and both legs, as for example from muscular dystrophy.

Quadriplegia: Paralysis of all four limbs, both arms and both legs, as from a high spinal cord accident or stroke.

Qualitative: Having to do with quality. In contrast to quantitative (which pertains to quantity, the amount).

Quantitative: Having to do with quantity or with the amount.

Quarantine: The period of isolation decreed to control the spread of infectious disease. Before the era of antibiotics and the like, quarantine as one of the few available means for halting the reach of infectious diseases. The word quarantine comes from the Latin quadraginta meaning forty. This was probably because it was known that the incubation period of most infectious diseases was less than 40 days.

Quasi-: Prefix meaning seemingly.

Quasidiploid: Seems to have the usual two full sets of 23 chromosomes and so to have a normal chromosome complement, but on closer examination, this is not so. Many malignant cells are quasidiploid. Also called pseudodiploid.

Quasidominant: Pattern of inheritance that seems due to a dominant trait but, in fact, is due to the mating of a person who has a recessive disorder (with 2 copies of a gene causing the disease) with someone who is an asymtomatic carrier ( and has 1 copy of the same gene buut no symptoms).

Queensland tick typhus: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.

Quickening: This apt word refers to the miraculous moment during pregnancy when the baby is first felt to move. Quickening has been used in this sense in the English language since 1530.

Quiescent: Inactive, resting. Tuberculosis might be quiescent (inactive).

Quinacrine: An antimalarial drug and, in cytogenetics, a fluorescent dye used to stain chromosomes. The Y chromosome stains brilliantly with quinacrine.

Quincke's disease: This is angioneurotic edema (or angioedema), a form of localized swelling of the deeper layers of the skin and fatty tissues beneath the skin. Hereditary angioneurotic edema (or hereditary angioedema) is a genetic form of angioedema. Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks.

Quinine: A classic antimalarial agent, quinine took its name from the Peruvian Indian kina meaning bark of the tree (they called it the fever tree), the cinchona tree from which quinine was first gained.

Quinsy: Not a TV detective but an old word for a peritonsillar abscess.

Quintan fever: A louse-borne disease first recognized in the trenches of World War I (and so called trench fever), again a major problem in the military in World War II, seen endemically in Mexico, N. Africa, E, Europe, and elsewhere. The cause, Rochalimaea quintana, is an unusual rickettsia that multiplies in the gut of the body louse. Transmission to people can occur by rubbing infected louse feces into abraded (scuffed) skin or conjunctiva (whites of the eyes). Onset of symptoms is sudden, with high fever, headache, back and leg pain and a fleeting rash. Recovery takes a month or more. Relapses are common. Quintan means recurring every 5 days and refers to the fever. Also called five-day fever. Other names include Wolhynia fever, shin bone fever, Meuse fever, His’ disease, His-Werner disease, Werner-His disease.

Quotidian: Recurring each day, as in a fever that returns every day. From the Latin quotidianus for daily. (In French, the noun quotidien is a daily newspaper.

Quotient: The result of mathematical division. The I.Q. (Intelligence Quotient) is arrived at by dividing the person's mental age (as determined on the Binet test) by the person's chronologic age and multiplying by 100. So if a child scores at the 8-year old level but is only 6, the I.Q. is 8/6 X 100=125.