Resources

List by Alphabet: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

a Related Biological Terms:

differential PCR display

A method for identification of mRNAs produced under specific physiological conditions. Total cellular RNA is reverse-transcribed, and the resultant cDNAs are used as templates for PCR. The 3'-primer has a poly(T) sequence that directs it to the poly(A) tail of mRNA, and is 5'-ended with two bases that make this primer more selective. (The two bases may be varied to achieve different selections.) The 5'-primer is short and of arbitrary sequence, and is intended to allow, under controlled non-stringent reannealing conditions of temperature, concentration, time, etc., amplification of a manageable number of specific cDNAs (between 50 and 100 bands) that can be electrophoretically separated on a DNA sequencing gel. The ladder of cDNAs can be displayed side-by-side with the cDNAs derived from cells in a different physiological state. This allows the identification of unique cDNAs that can be extracted, amplified by PCR, sequenced and identified. In a variant version called RNA fingerprinting arbitrary primer PCR (RAP-PCR), no poly(T) primer is used; one primer can serve for each of the two transcribed strands and the non-stringent reannealing conditions allow a fit to a manageable number of sites on the cDNA template.Liang, P. and Pardee, A. (1992) Science 257, 967-971; McClelland, M., Mathieu-Daude, F. and Welsh, J. (1995) Trends Genet. 11, 242-246 Related tool: real time pcr

differential centrifugation

The fractionation of subcellular components according to their sedimentation behaviour; separation into nuclei, mitochondria, lysosomes, microsomes (endoplasmic reticulum), ribosomes, cytosol, etc. by removal of sedimenting material after cycles of processing at progressively increasing centrifugal force.

differential chemical modification

(= competitive labelling (differential chemical modification))

differential genome display

A method for identifying candidate genes that may determine significant differences between closely related species whose genomes have been mapped, e.g. between a pathogen and a closely related non-pathogenic bacterium. The genome of one species is displayed as a circle showing at points on its circumference the genes. The genes are assigned a colour code according to a priority of similarities between the species: closely homologous genes are selected first, then the less closely related, then those of the remaining genes that have other known functions (viral proteins, bacterium–host interaction factors) until finally the unknown candidate genes remain. The display may also show a smaller concentric circles which display G/C content or other potentially relevant information.Huynen, M.A., Diaz-Lazcoz, Y. and Bork, P. (1997) Trends Genet. 13, 389-390 Recommended reading: next generation sequencing

differential hybridization

A method for comparison of different organs, or physiological or disease states by the genes that are uniquely expressed in them. The mRNAs of two types of cell to be compared, e.g. normal and cancer cells, are isolated, differently labelled for detection and hybridized to an appropriate cDNA library, preferably a normalized library. The library can be in the form of clones blotted onto duplicate filter membranes and the two sets of mRNAs, or can be labelled with two different radioisotopes, so that a clones that are equally labelled on both membranes identify a gene that is expressed equally in both kinds of cell, and a clone that fails to appear on one membrane will indicate transcription in only the other type of cell. A more sophisticated version labels the mRNAs with two different fluorophores, e.g. red emission for cancer cells and green emission for normal cells, so that when they are hybridized to the cDNA library that is arrayed in a relative excess on a single glass surface, the hybridization of both fluorophores to a single cDNA fragment will appear yellow, while the hybridization of only one, e.g. the normal cell mRNA, will appear green.Ito, T. and Sakaki, Y. (1996) Essays Biochem. 31, 11-21 Learn more about sgRNA.

differential reassociation

(see subtractive DNA cloning)

differentially methylated region (DAR)

see imprinting

diffraction pattern

The array of reflections obtained by crystallography. Each reflection indicates an intensity and, by its location, the angle with respect to the incident beam. Because a sharp pattern requires the wavelength of the incident beam to be of the same order of magnitude as the regular spacings, determination of inter-atomic distances is performed by X-ray crystallography, and the X-ray diffraction pattern is used to construct a three-dimensional model of the crystal. (see also subtractive DNA cloning) Learn more about genetic code table.

diketopiperazine

A six-membered heterocyclic product of the condensation of two -amino acids that contains amide bonds between the two -amino and the two -carboxy groups.

dioxygenase

An enzyme that reduces molecular oxygen by incorporating both atoms into its substrate, e.g. tryptophan dioxygenase. (see also mixed-function oxidase (mono-oxygenase))

< 56 57 58 59 60 61 62 63 64 65 66 > Total Pages 251

If you know of any terms that have been omitted from this glossary that you feel would be useful to include, please send detail to the Editorial Office at GenScript: website@genscript.com

If your term is adopted, we will send 1,000 EzCoupon points to your GenScript account.