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Nucleic acid analogues are compounds which are analogous (structurally similar) to naturally occurring RNA and DNA, used in medicine and in molecular biology research. Nucleic acids are chains of nucleotides, which are composed of three parts: a phosphate backbone, a pentose sugar, either ribose or deoxyribose, and one of four nucleobases.
For example, the wings of insects and birds evolved independently in widely separated groups, and converged functionally to support powered flight, so they are analogous. Similarly, the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures.
An example of a substrate analog that is also a suicide substrate/Trojan horse substrate is penicillin, which is an inhibitory substrate analog of peptidoglycan. [ 8 ] Some substrate analogs can still allow the enzyme to synthesize a product despite the enzyme’s inability to metabolize the substrate analog.
These agents can be used against hepatitis B virus, hepatitis C virus, herpes simplex, and HIV.Once they are phosphorylated, they work as antimetabolites by being similar enough to nucleotides to be incorporated into growing DNA strands; but they act as chain terminators and stop viral DNA polymerase.
The example above is an example alloparalogy. Symparalogs are paralogs that evolved from gene duplication of paralogous genes in subsequent speciation events. From the example above, if the descendant with genes A1 and B underwent another speciation event where gene A1 duplicated, the new species would have genes B, A1a, and A1b.
The recurrent evolution of flight is a classic example, as flying insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are analogous , whereas homologous structures or traits have a common origin but can have dissimilar functions.
Analogous structures - structures similar in different organisms because, in convergent evolution, they evolved in a similar environment, rather than were inherited from a recent common ancestor. They usually serve the same or similar purposes. An example is the streamlined torpedo body shape of porpoises and sharks. So even though they evolved ...
Pseudogenes are usually characterized by a combination of similarity or homology to a known gene, together with a loss of some functionality. That is, although every pseudogene has a DNA sequence that is similar to some functional gene, they are usually unable to produce functional final protein products. [1]