Nucleic acid structureNucleic acid structure refers to the structure of nucleic acids such as DNA and RNA. Chemically speaking, DNA and RNA are very similar. Nucleic acid structure is often divided into four different levels: primary, secondary, tertiary, and quaternary. Nucleic acid sequence Primary structure consists of a linear sequence of nucleotides that are linked together by phosphodiester bond. It is this linear sequence of nucleotides that make up the primary structure of DNA or RNA.
Homology (biology)In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor.
Mycolic acidMycolic acids are long fatty acids found in the cell walls of the Mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species. Despite their name, mycolic acids have no biological link to fungi; the name arises from the filamentous appearance their presence gives mycolata under high magnification. The presence of mycolic acids in the cell wall also gives mycolata a distinct gross morphological trait known as "cording".
Motif (music)In music, a motif IPA: (/moʊˈtiːf/) (also motive) is a short musical idea, a salient recurring figure, musical fragment or succession of notes that has some special importance in or is characteristic of a composition. The motif is the smallest structural unit possessing thematic identity. The Encyclopédie de la Pléiade regards it as a "melodic, rhythmic, or harmonic cell", whereas the 1958 Encyclopédie Fasquelle maintains that it may contain one or more cells, though it remains the smallest analyzable element or phrase within a subject.
LeitmotifA leitmotif or leitmotiv (ˌlaɪtmoʊˈtiːf) is a "short, recurring musical phrase" associated with a particular person, place, or idea. It is closely related to the musical concepts of idée fixe or motto-theme. The spelling leitmotif is an anglicization of the German Leitmotiv (ˈlaɪtmoˌtiːf), literally meaning "leading motif", or "guiding motif". A musical motif has been defined as a "short musical idea ...
