A nucleus, cell (usually reproductive) or organism having a single set or copy of unpaired chromosomes. Gametes, formed as a result of meiosis, are haploid in that the number of chromosomes is halved randomly. Fusion of two reproductive cells during fertilization restores the normal diploid number of chromosomes (viz., 46) as shown in the figure …
Category Archives: Uncategorized
Haploinsufficiency
Genetic mutations that result in half the normal level of the gene product leading to phenotypic effects (i.e., they are sensitive to gene dosage). It occurs in individuals who are heterozygous for a certain gene mutation or homozygous at a particular locus, often due to a deletion of the corresponding allele. Turner’s syndrome is thought …
Handicap
A physical, mental, or emotional condition that interferes with an individual’s normal (everyday) functioning. Reduction in a person’s capacity to fulfill a social role as a consequence of an impairment, inadequate training for the role, or other circumstances. See Cerebral palsy, Disability, Impairment, Normality
Handedness (bimanual versus unimanual)
This distinction refers to: 1. the hand that performs faster or more precisely on manual tasks; and 2. the hand preferred for use, regardless of performance. In addition, there is another ongoing debate about how many types of handedness there are: right versus left, right versus non-right, and whether or not ambidexterity should be included. Handedness …
Handedness (general)
A vague term that has a number of interpretations. In general, it refers to the tendency to use one hand more often and more proficiently on a wide range of tasks requiring speed, precision, force, and skill, especially on tasks requiring controlled, or modulated, force and the coordination of complex sequences of movements of the …
Hand proficiency
Refers to the skill and/or speed in performance in which one hand is better than the other. See Ambidexterity, Bimanual task, Finger-tapping task, Hand preference, Handedness (bimanual versus unimanual), Handedness (general), Lateral bias, Peg-moving task
Haemophilus influenza type B (Hib)
Previously called Pfeiffer’s bacillus after Richard Pfeiffer (1858-1945) who first described in 1892, it is a species of rod-shaped, gram-negative bacteria that is the major cause of bacterial meningitis and acute epiglottitis, as well as pneumonia, in young children (with more than 90% of all Hib infections occurring in children of 5 years of age …
Hand preference
Refers to the tendency to use one hand more often, or preferentially, for one or more activities. It may or may not typify preference for all tasks. Furthermore, it does not necessarily mean that the preferred hand is more proficient. See Ambidexterity, Bimanual task, Delivery position (presentation), Finger-tapping task, Hand proficiency, Handedness (bimanual versus unimanual), …
Habitat (ecology)
The physical and chemical features of the local environment in which a plant or an animal lives. See Community (ecology), Ecology, Ecosystem, Environment, Ethology, Ethnography, Evolutionary niche theory, Niche (ecology), Umwelt
Habituation
A decrease in responding to the repeated presentation of a particular stimulus (see figure below). Habituation to a specific stimulus is generally believed to reflect the progressive encoding of that stimulus in memory and to be a simple form of learning. A representation of habituation occurring to the repeated presentation of a visual display over …