Inheritance pattern requiring the influence of several (four or more) genes. The inheritance of characters such as height, weight and behavior depends on the simultaneous action of a number of genes in interaction with the environment. It is a form of inheritance that increases the probability that a character or trait will show continuous variation …
Category Archives: Uncategorized
Polycyclic aromatic hydrocarbons
A group of over 100 different chemicals that form during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco. In recent years, car exhaust fumes, especially from diesel fuel have been identified as a major health risk for both prenatal and postnatal development. See Environmental tobacco smoke (ETS)
Poisson distribution
Named after Siméon-Denis Poisson (1781-1840), it is a skewed probability distribution with a long tail representing the number of randomly occurring events with a constant mean rate in a specified time interval. Its most frequent use is to model the random occurrence of infrequent events that have a fixed probability of occurrence. It has also been used …
Polarizer
Signalling molecule that designates the front or back of a structure in early development. For example, a zone of polarizing activity was discovered the 1960s, which has been shown to at acts as organizer that mediates cell-to-cell interactions responsible for limb patterning in vertebrate embryos See Cytokines, Growth cones, Lipids, Maturational gradients, Neurulation, Retinoic acid (RA
Plosive
See Babbling, Bilabial, Clicks, Consonants, Fricative, Glottal, Labio-dental, Lateral sound, Lingua-alveolar (or alveolar), Lingua-ental (or dental), Lingua-palatal (or palatal), Rhotic sound
Point-light display
introduced by Gunnar Johansson (1911-1998) in 1973, it typically consists of small light sources or reflective markers attached to the main joints of the body, especially, the elbows, wrists, hips, knees and ankles. As the person moves in a darkened environment dressed completely in black, an almost immediate impression is created of a coherent and recognisable movement …
Plial surface
See Cell migration, Plexus
Pleonastic extensions
An overgeneralization of a word that uses not only perceptual features, but also fortuitous event conjunctions, such as referring to a lake as a ‘duck’ because sometimes ducks are found there. See Language development, Overgenealization, Undergeneralization
Plexus
In medical terminology, it is a network or interweaving (anastomosing) of nerves (most commonly axons outside the central nervous system, an exception being the choroid plexus)) and blood vessels. The main plexuses are the brachial, cervical, lumbar and sacral plexuses. See Brachial plexus, Cell migration, Lumbosacral plexus, Plial surface
Pleasure-pain principle
Governed by the id, it refers to the gratification of needs and the avoidance (or discharge) of unpleasurable tensions by means of, for example, hallucinations and fantasy. Originally, introduced by Sigmund Freud (1856-1939) as the unpleasure principle from the German word Lustprinzip, it is associated with a primitive id function in infant development during which …