Harpers

MOLECULAR GENETICS, RECOMBINANT DNA, & GENOMIC TECHNOLOGY / 413also be used to study the function of a certain fragmentof DNA and to analyze how genes are regulated.• Chimeric DNA molecules are introduced into cellsto make transfected cells or into the fertilized oocyteto make transgenic animals.• Techniques involving cloned DNA are used to locategenes to specific regions of chromosomes, to identifythe genes responsible for diseases, to study how faultygene regulation causes disease, to diagnose geneticdiseases, and increasingly to treat genetic diseases.GLOSSARYARS: Autonomously replicating sequence; the originof replication in yeast.Autoradiography: The detection of radioactivemolecules (eg, DNA, RNA, protein) by visualizationof their effects on photographic film.Bacteriophage: A virus that infects a bacterium.Blunt-ended DNA: Two strands of a DNA duplexhaving ends that are flush with each other.cDNA: A single-stranded DNA molecule that iscomplementary to an mRNA molecule and is synthesizedfrom it by the action of reverse transcriptase.Chimeric molecule: A molecule (eg, DNA, RNA,protein) containing sequences derived from twodifferent species.Clone: A large number of organisms, cells or moleculesthat are identical with a single parental organismcell or molecule.Cosmid: A plasmid into which the DNA sequencesfrom bacteriophage lambda that are necessary forthe packaging of DNA (cos sites) have been inserted;this permits the plasmid DNA to be packagedin vitro.Endonuclease: An enzyme that cleaves internalbonds in DNA or RNA.Excinuclease: The excision nuclease involved in nucleotideexchange repair of DNA.Exon: The sequence of a gene that is represented(expressed) as mRNA.Exonuclease: An enzyme that cleaves nucleotidesfrom either the 3′ or 5′ ends of DNA or RNA.Fingerprinting: The use of RFLPs or repeat sequenceDNA to establish a unique pattern ofDNA fragments for an individual.Footprinting: DNA with protein bound is resistantto digestion by DNase enzymes. When a sequencingreaction is performed using such DNA, a protectedarea, representing the “footprint” of thebound protein, will be detected.Hairpin: A double-helical stretch formed by basepairing between neighboring complementary sequencesof a single strand of DNA or RNA.Hybridization: The specific reassociation of complementarystrands of nucleic acids (DNA withDNA, DNA with RNA, or RNA with RNA).Insert: An additional length of base pairs in DNA,generally introduced by the techniques of recombinantDNA technology.Intron: The sequence of a gene that is transcribedbut excised before translation.Library: A collection of cloned fragments that representsthe entire genome. Libraries may be eithergenomic DNA (in which both introns and exonsare represented) or cDNA (in which only exonsare represented).Ligation: The enzyme-catalyzed joining in phosphodiesterlinkage of two stretches of DNA orRNA into one; the respective enzymes are DNAand RNA ligases.Lines: Long interspersed repeat sequences.Microsatellite polymorphism: Heterozygosity of acertain microsatellite repeat in an individual.Microsatellite repeat sequences: Dispersed orgroup repeat sequences of 2–5 bp repeated up to50 times. May occur at 50–100 thousand locationsin the genome.Nick translation: A technique for labeling DNAbased on the ability of the DNA polymerase fromE coli to degrade a strand of DNA that has beennicked and then to resynthesize the strand; if a radioactivenucleoside triphosphate is employed, therebuilt strand becomes labeled and can be used asa radioactive probe.Northern blot: A method for transferring RNAfrom an agarose gel to a nitrocellulose filter, onwhich the RNA can be detected by a suitableprobe.Oligonucleotide: A short, defined sequence of nucleotidesjoined together in the typical phosphodiesterlinkage.Ori: The origin of DNA replication.PAC: A high capacity (70–95 kb) cloning vectorbased upon the lytic E. coli bacteriophage P1 thatreplicates in bacteria as an extrachromosomal element.Palindrome: A sequence of duplex DNA that is thesame when the two strands are read in opposite directions.Plasmid: A small, extrachromosomal, circular moleculeof DNA that replicates independently of thehost DNA.Polymerase chain reaction (PCR): An enzymaticmethod for the repeated copying (and thus amplification)of the two strands of DNA that make upa particular gene sequence.