| LF | labile factor; lactoferrin; laryngofissure; Lassa fever; latex fixation; left foot; left forearm; le... |
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| LT | heat-labile toxin; laminar tomography; left; left thigh; less than; lethal time; leukotriene; Levin ... |
| OALF | organic acid labile fluid |
| DNA insertion elements | Discrete transposable segments of DNA which can insert into chromosomal, phage, and plasmid DNA. Some insert at random while others are site-specific; most have not been found to exist except in the inserted state. Their insertion into a genome always produces a mutation ("insertion mutation"), and their excision frequently results in a loss of host genetic information. Types of transposable elements include is elements (insertion sequence elements), which are composed of between 700 and 1400 bases and contain no genes unrelated to insertion function and tn elements (transposon elements), which are generally larger than 1400 bases and contain genes unrelated to insertion function. The concept also includes the delta element of saccharomyces cerevisiae and the integration site. (12 Dec 1998) |
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| elements | Simple substances which cannot be decomposed by chemical means. They are made up of atoms which are alike in their peripheral electronic configurations, their chemical properties, and in the number of protons in their nuclei. They may differ in the number of neutrons in their nuclei. (12 Dec 1998) |
| elements, radioactive | Chemical elements which spontaneously transmute into another element with corpuscular or electromagnetic radiation. The natural radioactive elements are all those with an atomic number above 83, and some other elements, such as potassium (atomic number 19) and rubidium (atomic number 7), which are very weakly radioactive. (12 Dec 1998) |
| trace elements | A group of chemical elements that are needed in minute quantities for the proper growth, development, and physiology of an organism. (12 Dec 1998) |
| fold-back elements | A type of transposable element that possesses long inverted repeats, such that when denatured, loops are formed. (05 Mar 2000) |
| long interspersed elements | Long repetitive sequences in DNA with terminal repeats seen in human and mouse DNA. (05 Mar 2000) |