Genetics Key Terms 4

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ampicillin

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beta-lactam antibiotic that has been used to treat bacterial infections since 1961.

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ampicillin resistance gene

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commonly used as a selectable marker in routine biotechnology. The enzyme responsible for degrading ampicillin is called beta-lactamase, in reference to the beta-lactam structure of ampicillin and related drugs.

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cDNA(complementary DNA)

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DNA synthesized from an RNA template by the enzyme reverse transcriptase.

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clone

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Identical molecules, cells, or organisms derived from a single ancestor by asexual or parasexual methods. For example, a DNA segment that has been inserted into a plasmid or chromosome of a phage or a bacterium and replicated to produce many copies, or an organism of identiical genetic composition to that used in its production.

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denaturation

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a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent, or heat. In DNA molecules, they are seperated into single strands.

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dideoxynucleotide

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A nucleotide containing a deoxyribose sugar lacking a 3' hydroxyl group. It stops further chain elongation when incorporated into a growing polynucleotide and is used in the Sanger method of DNA sequencing.

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Sanger sequencing

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developed in 1975. modernized DNA sequencing

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genomic library

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a collection of clones that contains all the DNA sequences of an organism's genome.

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IPTG

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molecular biology reagent. used to mimic allolactose, a lactose metabolite that triggers transcription of the lac operon. IPTG also induces the transcription of the gene coding for beta-galactosidase, a hydrolase enzyme that catalyzes the hydrolysis of B=galactosides into monosaccharides.

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ligation (DNA ligase)

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An enzyme that forms a covalent bond between the 5' end of one polynucleotide chain and the 3' end of another polynucleotide chain. It is also called polynucleotide-joining enzyme.

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origin of replication

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Sites where DNA replication begins alson the length of the chromosome.

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PCR(polymerase chain reaction)

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A method for amplifying DNA segments that depends on repeated cycles of denaturation, primers, and DNA polymerase-directed DNA synthesis.

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primer (oligonucleotide primer)

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In nucleic acids, a short length of RNA or single-stranded DNA required for the initiating synthesis directed by polymerases.

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primer annealing

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causes primer to bind to denatured, single-stranded DNA. annealing temperature is between 50-70 C.

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polylinker

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A segment of DNA that has been engineered to contain multiple sites for restriction enzyme digestion. Polylinkers are usually found in engineered vectors such as plasmids.

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probe

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A macromolecule such as DNA or RNA that has been labeled and can be detected by an assay such as autoradiography or fluorescence microscopy. Probes are used to identify target molecules, genes, or gene products.

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pUC (plasmid vector)

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In recombinant DNA, an agent such as a phage or plasmid into which a foreign DNA segment will be inserted and utilized to transfrom host cells.

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pulsed-field gel electrophoresis

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A technique used for the seperation of large DNA molecules by applying an electric field that periodically changes direction to a gel matrix.

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recombinant DNA

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A DNA molecule formed by joining two heterologous molecules. A term also applied to the technology associated with the use of DNA molecules produced by in vitro ligation of DNA from two different organisms.

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recombinant DNA molecule

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DNA from two or more sources are incorporated into a single recombinant molecule

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recombinant vector

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Formation of recombinant DNA requires a cloning vector, a DNA molecule that will replicate within a living cell.

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restriction enzyme

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cuts double-stranded or single-stranded DNA at specific recognition nucleotide sequences known as restriction sites. They are thought to have evolved to provide a defense mechanism against invading viruses.

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restriction fragment

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a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme, a process called restriction.

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restriction map

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a map of known restriction sites within a sequence of DNA.

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restriction sequence

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locations on a DNA molecule containing specific sequences of nucleotides, which are recognized by restriction enzymes.

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southern blot

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a method routinely used in molecular biology for detection of a specific DNA sequence in DNA samples. Combines transfer of electrophoresis-seperated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization.

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Taq polymerase

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a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquticus from which it was originally isolated. Frequently used in PCR, a method for greatly amplifying short segments.

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X-gal

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an organic compound consisting of galactose linked to a substituted indole. It is very heavily used in molecular biology.

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hybridization

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an individual produced by crossing parents from two different genetic composition or strains..

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sedimentation equilibrium centrifugation

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The equilibrium between the forward movement of a sample's liquid-sediment boundary and reverse diffusion during centrifugation.

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sedimentation velocity centrifugation

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uses ultraviolet absorption optics to monitor the migration of the molecules during centrifugation and determine the "velocity of sedimentation". Velocity standardized in units called Svedburg coefficients (S).

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hyperchromic shift

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The striking increase in absorbance of DNA

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melting temperature

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The temperature at which a population of double-stranded nucleic acid molecules is half-dissociated into single strands.

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molecular hybridization

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not sure yet

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FISH(fluorescence in situ hybridization)

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A method of in situ hybridization that utilizes probes labeled with a fluorescent tag, causing the site of hybridization to fluoresce when viewed using ultraviolet light.

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agarose gel electrophoresis

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a method of gel electrophoresis usedin clinical chemistry to seperate proteins by charge and or size and in biochemistry and molecular biology to seperate a mixed population of DNA and RNA fragments by length.

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satellite DNA

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DNA that forms a minor band when genomic DNA is centrifuged in a cesium salt gradient. This DNA usually consists of short sequences repeated many times in the genome.