Q

Q bandings

A staining technique in which metaphase chromosomes are stained with quinacrine mustard to produce temporary fluorescent Q bands on the chromosomes.

Quadrant

One of the quarters of the plane of the Cartesian coordinate system

Quadrantanopia

Defect in vision or blindness in one fourth of the visual field.

Quadratic equation

An equation involving the second power, but no higher power of an unknown.   The general form of a quadratic equation in two unknowns is:
Ax2 + Bxy + Cy2 + Dx + Ey + F = 0.

Quadratic formula

The formula that says that the solution to the equation ax2 + bx + c = 0 is:

Quadriplegia

Paralysis or partial paralysis of all four limbs of the body (both arms
and both legs). The legs are usually affected more than the arms.

Quadrilateral

A polygon with 4 sides.
Examples:
rectangle: a quadrilateral with four 90 degree angles.
rhombus: a quadrilateral with four equal sides.
square: a quadrilateral with four equal sides and four 90 degree angles.
trapezoid: a quadrilateral that has exactly two sides parallel.

Qualia

A property of self, of experiencing the environment such as colors, tastes, or pain. The qualia refers to a part of consciousness that is different from the physical nature of the stimulus that provokes it. For example, in describing a color - red, blue, or green - we talk about a qualia of an object. The physical existence of a color is a quantum mechanical state that emits energy in from of electromagnetic radiation that is decoded by our sensory organs - the eye and the visual cortex in the brain as red, blue, or green. We have no a priori knowledge if these colors exists independent of us. We can only assert that the radiation has a certain energy who's quanta (the single photon) can elicit quantum mechanical effect in the retinal cell layer of our eyes.

Qualitative

A non-numerical description of a situation. Compare to quantitative

Quality Assurance

Quality assurance is a comparison between the control parameters from a group of current data runs and the corresponding parameters from the reference data runs.

Quality Control

Quality control is a comparison between the control parameters from one data run and the corresponding parameters from the reference runs.

Quantal release

The concept that neurotransmitter is secreted in discrete amounts called quanta.A quanta of neurotransmitter is generally held to be the amount of transmitter stored in a single vesicle.

Quantitative

A numerical description of a situation.Compare to qualitative

Quantum theory

The theory that energy can only be absorbed or radiated in discrete values or quanta. 
All particles are subject to quantum theory.

Quantitative character

A heritable feature in a population that varies continuously as a result of environmental influences and the additive effect of two or more genes (polygenic inheritance).

Quantitative descriptive analysis (QDA)

Description of the intensity of the attributes of a sample.

Quantitative-fluorescent polymerase chain reaction (QF-PCR)

A technique based on the use of the polymerase chain reaction to amplify, in a quantitative way, highly polymorphic tracts of repeated sequence that are specific for particular chromosomes. A fluorochrome is incorporated in the amplified products of the PCR so that they can be detected by a DNA scanner. Most individuals are heterozygous for the polymorphic repeat alleles, so each locus appears as two separate peaks on the scan. A trisomic individual will usually show, for each locus on the trisomic chromosome, three equal peaks or two peaks of which one is twice the size of the other.

Quantitative Reverse Transcriptase Polymerase Chain Reaction (Q-RT PCR)

A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The cDNA is then amplified using standard PCR protocols.

Quantitative Structure-Activity Relationship (QSAR)

A computer modeling technique that enables researchers (e.g., drug development chemists) to predict the likely activity (e.g., effect on tissue) of a new compound before that compound is actually created. Invented in 1963 by Corwin Hasch. QSAR is based on data from decades of research investigating the impact on "activity" of the chemical structures of thousands of thoroughly-studied molecules.For example, the biological activity (i.e., bacteria-killing effectiveness) of most antibiotics correlates with their tendency to dimerize (i.e., link two molecules into a single molecular unit).
See also SAR by NMR.

Quantitative Structure-Property Relationship (QSPR)

A computer modeling technique which enables scientists to predict the likely properties of a new chemical compound before that chemical compound is actually created.

Quantization

In its original meaning, quantization is the step of passing from a continuous to a discrete variable, like in analogue-to-digital signal conversion. More generally, the term can be used for any method decreasing the precision of representation by eliminating part of the information. Applied to image compaction, quantization describes a step of eliminating or reducing the relevance of coefficients that carry little information (a different, analogous quantization is found in the thresholding of coefficients in principal component analysis). A typical compression step used for images transforms a (sub-)image, e.g. an 8x8 pixel matrix, by a discrete cosine transform, then uses a quantization step which consists of a suitable linear combination of the transformed pixels (i.e. in the ``frequency domain''), and then uses Huffman coding for the resulting information. Except for quantization, these steps have a clearly defined inversion, so that in the definition of the quantization matrix the key criterion is the quality difference between the original and the encoded/decoded image.

Quantitative trait

A measurable trait that shows continuous variation; a trait that can not be classified into a few discrete classes.

Quantitative trait locus

A gene affecting the phenotypic variation in continuously varying traits like skin color, weight, etc.

Quantum Mechanics

The physical theory of the composition and behavior of atoms and subatomic particles; explains the duality of light as wave and particle, the existence of chemical bonds, and radioactivity.

Quaternary Structure

The highest level of organization within a protein complex that describes the number of subunits (individual polypeptide chains) and their interactions. It thus describes the organization of protein complexes as dimers (two subunits), trimers (three subunits), tetramers (four subunits) and so on. The lower levels are tertiary structure (of each subunit or individual polypeptide), the secondary structure (local regular repeats in polypeptide folding) and primary structure (sequence).

Quarks

Fundamental particles, incapable of  independent existence, that combine to form particles such as protons and neutrons.

Quaternary structure

The association of polypeptide subunits to form the final structure of a protein.
The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.

Quartic

A polynomial of degree 4.

Quintic

A polynomial of degree 5.

Quelling

Refers to the impact (on gene expression) of RNA interference.

Quinone

An enzymatic cofactor that plays an important role in photosynthesis and respiration. More specifically, it is part of the electron transport chain in mitochondria and chloroplast membranes.

Quotient

The answer to a division problem.