A series of triplet codons beginning from a specific nucleotide. Depending on where one begins, each DNA strand contains three different reading frames. (See Open reading frame, Overlapping reading frames.)

Characterized as having a phenotype expressed only when both copies of the gene are mutated or missing.

A single copy of this gene is sufficient to suppress cell proliferation; the loss of both copies of the gene contributes to cancer formation. (See Oncogene.)

A nucleotide sequence--composed typically of 4, 6, or 8 nucleotides--that is recognized by a restriction endonuclease. Type II enzyrnes cut (and their corresponding modification enzymes methylate) within or very near the recognition sequence.

A cell that results from recombination of genes.

The process of cutting and recombining DNA fragments from different sources as a means to isolate genes or to alter their structure and function.

The frequency at which crossing over occurs between two chromosomal loci--the probability that two loci will become unlinked during meiosis.

A gene whose protein controls the activity of other genes or metabolic pathways.

See Plasmid.

A plasmid that replicates independently of the main bacterial chromosome and is present in 10-500 copies per cell. (See Plasmid.)

The reannealing (hydrogen bonding) of single- stranded DNA and/or RNA to form a duplex molecule.

A chromosomal region containing the DNA sequences necessary to initiate DNA replication processes.

A DNA-binding protein in prokaryotes that blocks gene transcription by binding to the operator.

A class of endonucleases that cleaves DNA after recognizing a specific sequence, such as BamH1 (GGATCC), EcoRI (GAATTC), and HindIII (AAGCTT). Type I. Cuts nonspecifically a distance greater than 1000 bp from its recognition sequence and contains both restriction and methylation activities. Type II. Cuts at or near a short, and often symmetrical, recognition sequence. A separate enzyme methylates the same recognition sequence. Type III. Cuts 24-26 bp downstream from a short, asymmetrical recognition sequence. Requires ATP and contains both restriction and methylation activities.

See Mapping.

Differences in nucleotide sequence between alleles at a chromosomal locus result in restriction fragments of varying lengths detected by Southern analysis.

A member of a class of RNA viruses that utilizes the enzyme reverse transcriptase to reverse copy its genome into a DNA intermediate, which integrates into the hostcell chromosome. Many naturally occurring cancers of vertebrate animals are caused by retroviruses.

Using linkage analysis and polymorphic markers to isolate a disease gene in the absence of a known metabolic defect, then using the DNA sequence of the cloned gene to predict the amino acid sequence of its encoded protein.

An enzyme isolated from retrovirus-infected cells that synthesizes a complementary (c)DNA strand from an RNA template.

See Restriction-fragment-length polymorphism.

Bacteria in a symbiotic relationship with leguminous plants that results in nitrogen fixation. See Nitrogen fixation.

The soils region on and around plant roots.

The RNA component of the ribosome. (See RNA.)

Cellular organelle that is the site of protein synthesis during translation. See Organelle, Translation.

The region of an mRNA molecule that binds the ribosome to initiate translation.

See Catalytic RNA.

An organic acid composed of re- peating nucleotide units of adenine, guanine, cytosine, and uracil, whose ribose components are linked by phosphodiester bonds. (See Antisense RNA, Heterogeneous nuclear RNA, Messenger RNA, Ribosomal RNA, RNA polymerase, Small nuclear RNA, Transfer RNA.)

Transcribes RNA from a DNA template. (See Polymerase, RNA.)

See Ribosomal RNA.