modification


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Related to modification: behavior modification

modification

[‚mäd·ə·fə′kā·shən]
(cell and molecular biology)
In nucleic acid metabolism, any changes made to deoxyribonucleic acid or ribonucleic acid after their original incorporation into a polynucleotide chain.
(engineering)
A major or minor change in the design of an item, effected in order to correct a deficiency, to facilitate production, or to improve operational effectiveness.
(metallurgy)
Treatment of molten aluminum alloys containing 8-13% silicon with small amounts of a sodium fluoride or sodium chloride mixture; improves mechanical properties.
(science and technology)
Any change brought about by external or internal factors.

Modification

 

in biology, nonhereditary changes in the visible characters (phenotype) of an organism; these changes occur under the influence of altered environmental conditions.

Modifying factors in the environment (temperature, illumination, diet) act on the organism during sensitive periods of its development, precipitating changes in the organism’s internal makeup (for example, changes in hormone level) and altering the course of ontogeny. Modificational variation consists in changes within the limits of the genotypically conditioned norm of reaction. Depending on the temperature of its environment, the Himalayan rabbit may change from black in cold weather to rusty brown in mild temperatures to pure white in high temperatures. However, the coloration of the parent rabbits is not inherited by their young; only the capacity to change color according to temperature change is inherited.

In nature, modifications are, as a rule, adaptive reactions of organisms to environmental factors. Thus, in lake Sagittaria sagittifolia, the shape of the leaves depends on where they grow: the above-water leaves are arrow-shaped, the leaves that float are heart-shaped with stomata on the upper side, and the underwater leaves are ribbon-like. Nonadaptive modifications often consist of all kinds of developmental disturbances, the extreme expression of which includes deformities and morphological and physiological malfunctions. These modifications occur, as a rule, in response to strong external stimuli, to which individuals of a given species are rarely exposed under normal conditions.

In contrast to mutations, modifications are not transmitted by heredity. Modifications develop in individuals of a given generation only when the conditions under which these modifications normally arise are present. However, in unicellular and occasionally multicellular organisms, prolonged modifications are found when changes in visible characters that have arisen as a result of environmental factors are retained for several generations, even after the disappearance of the inducing factors. This type of modification is apparently caused by changes in relatively stable self-reproducing cytoplasmic structures. Since they are nonhereditary, modifications have no direct evolutionary significance. If, however, a phenotype formed as a result of modification has a high adaptive value, the phenotype may become fixed in evolution only through the selection of those mutants that retain a given modification, but discard other modifications of a given character.

REFERENCES

Lobashev, M. E. Genetika, 2nd ed. Leningrad, 1967.
Shmal’gauzen, I. I. Faktory evoliutsii. Moscow, 1968.

N. V. TIMOFEEV-RESOVSKII, V. I. IVANOV and V. A. MGLINETS

modification

1. A written amendment to the contract document signed by both parties.
3. A written or graphic interpretation issued by the architect.
4. A written order for a minor change in the work, 1 issued by the architect.

modification

An alteration or change meant to rectify faults or shortcomings or which offers improved capability. A modification involves changes in the design of equipment or components.
References in periodicals archive ?
For more information about Fontaine Modification Vocational Services, call 800.
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Ahmad Bahrozyan, executive director of the RTA Licensing Agency, told 7DAYS: "We are considering a very important project in 2015 which will take us into the classification and certification of garages in Dubai, including garages that conduct vehicle modifications.
appropriation types used to fund modification work orders.
Bankers also complain that they have not been consulted about the modifications despite being directly concerned and wonder why the modifications are passed now although in 2010 the same provision was changed at their initiative.
However, lenders like Bank of America who, as of the June s Home Affordable Modification Program report had an estimated 469,905 homeowners who were delinquent on their home loan and potentially qualified for a home loan modification.
Behavior modification is focused on having a child respond appropriately to the demands of the formal power structure.
Inadequate modification can produce a semi-treated phase called lamellar silicon.
Current and future missions depend heavily on the aircraft's ability to find and track targets, so this modification to the synthetic aperture radar is critical.
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Once it appears the contract is renewable or extendable without substantial cost or modification, a useful life longer than the contract term is a defensible option for the company.
Some very basic modifications could increase the success for students with LD and also help others in the classroom that are at risk for having learning problems.