Glossary

Deoxyribose Nucleic Acid

The molecular basis for genes; every inherited characteristic has its origin somewhere in the code of the organism's complement of DNA. The code is made up of subunits, nucleic acids. The organism to produce the required proteins that compose the genetic traits of the organism and its life functions interprets the sequence of the four nucleic acids.

The molecule of which the genetic material is composed. It consists of two chains joined together as a double helix. Each chain is composed of a polymer of nucleotides (consisting of a nitrogenous base, a deoxyribosesugar ring, and a phosphate group) joined together by phosphodiester bonds between the 5’-phosphate of one nucleotide and the 3’-hydroxyl of the next. The two chains run in opposite directions and are held together by hydrogen bonds between the bases in equivalent positions in the two chains. There are various forms of double helical DNA. They are:1.B-DNA (first described by Crick and Watson) is a right-handed helix with 10.6 base pairs per turn and is probably the main form of cellular DNA.2.A-DNA is also a right-handed helix but is somewhat skewed and contains about 11 base pairs per turn. It is the form taken By DNA-RNA hybrid double helixes.3.Z-DNA is a left-handed helix with 11 base pairs per turn. It is favored by regions rich in guanine cutosine base pairs and probably occurs infrequently in cellular DNA.

Multiplication of a piece of DNA in a test-tube into many thousands of millions of copies. The most commonly used process is the polymerase chain reaction (PCR) system, but other systems are being developed, including ligase chain reaction (LCR), nucleic acids sequence-dependent amplification, and the Q-beta system.

Spots of DNA arranged on a slide support such as glass or silicon “DNA chip” (or microarray), used for screening, sequencing, genetic mapping, and so on.

A service that stores DNA extracted from blood samples or other human tissue.

A small piece of glass or silicon that has small pieces of DNA arrayed on its surface.

Sequences of nucleic acids in specific areas (loci) on a DNA molecule are polymorphic, meaning that the genes in those locations may differ from person to person. DNA fragments can be cut from those sequences using restriction enzymes. Fragments from various samples can be analyzed to determine whether they are from the same person. The technique of analyzing restriction fragment length polymorphism (RFLP) is called DNA typing or DNA fingerprinting.

The formation of a double-stranded nucleic acid molecule from two separate strands. The term also applies to a molecular technique that uses one nucleic acid strand to locate another.

A collection of cloned DNA fragments that collectively represent the genome of an organism.

A small glass surface to which has been fixed an array of DNA fragments, each with a defined location. A typical DNA chip would contain 10 000 discrete spots (each containing a different DNA fragment) in an area of just a few square centimeters. When a solution of fluorescently labelled DNA fragments is hybridized to the chip, spots to which hybridization occurs are visible as fluorescence. If the spots on the chip are genes (expressed sequence tags), hybridization with cDNA from a particular tissue shows which genes are expressed in that tissue. If the spots are short, synthesized oligonucleotides (approximately 25 bases) corresponding to that part of a gene containing a single nucleotide polymorphisms (SNP), with a separate spot for each of the 4 possible bases at that site, hybridization with genomic DNA from an individual plant or animal enables that individual to be genotyped at as many SNP loci as are represented on the chip. The big advantage of DNA chips is the extent to which the process of genotyping can be automated, thereby enabling huge numbers of plants or animals to be genotyped for a huge number of loci.

An enzyme that replicates DNA. DNA Polymerase is the basis of PCR - the Polymerase chain reaction.

A labeled (tagged) segment of DNA that is able, after a DNA hybridization reaction, to detect a specific DNA sequence in a mixture of sequences. If the tagged sequence is complementary to any one in the mixture, the two sequences will form a double helix. This will be identified thanks to its label (either by radioactivity or fluorescence).

Proteins that recognize and repair certain abnormalities in DNA.

The use of existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.

The relative order of base pairs, whether in a fragment of DNA, a gene, a chromosome, or an entire genome.

Procedures for determining the nucleotide sequence of a DNA fragment. There are two common methods for doing this:• The Maxam and Gilbert technique (chemical degradation), that uses different chemicals to break the DNA into fragments at specific bases; or• The Sanger technique (called the di-deoxy or chain-terminating method) uses DNA polymerase to make new DNA chains, with di-deoxy nucleotides (chain terminators) to stop the chain randomly as it grows.In both cases, the DNA fragments are separated according to length by polyacrylamide gel electrophoresis, enabling the sequence to be read directly from the gel.

A nucleic acid vaccine: Genes coding for specific antigenic proteins are injected to produce those antigens and trigger an immune response.

A DNA vehicle for transferring generic information from one cell to another.

Dense, Non-Aqueous Phase Liquids

An enzyme that degrades DNA.

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