A unit of measurement equal to the mass of a hydrogen atom, 1.67 x 10E-24 gram/L (Avogadro's number).

The final growth phase, during which nutrients have been depleted and cell number decreases. (See Growth phase).

To induce structural alterations that disrupt the biological activity of a molecule. Often refers to breaking hydrogen bonds between base pairs in double-stranded nucleic acid molecules to produce in single-stranded polynucleotides or altering the secondary and tertiary structure of a protein, destroying its activity.

High-speed centrifugation in which molecules "float" at a point where their density equals that in a gradient of cesium chloride or sucrose. (See Centrifugation.)

See DNA, nuclease.

A disease associated with the absence or reduced levels of insulin, a hormone essential for the transport of glucose to cells.

A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation. Dideoxynucleotides are used in DNA sequencing and the treatment of viral diseases. (See Nucleotide.)

See Dideoxynucleotide.

To cut DNA molecules with one or more restriction endonucleases.

A cell which contains two copies of each chromosome. See Haploid cell.

DNA insert and vector molecules are digested with two different restriction enzymes to create noncomplementary sticky ends at either end of each restriction fragment. This allows the insert to be ligated to the vector in a specific orientation and prevents the vector from recircularizing. (See Cloning.)

An organic acid and polymer composed of four nitrogenous bases--adenine, thymine, cytosine, and guanine linked via intervening units of phosphate and the pentose sugar deoxyribose. DNA is the genetic material of most organisms and usually exists as a double-stranded molecule in which two antiparallel strands are held together by hydrogen bonds between adeninethymine and cytosine-guanine. (See b-DNA, cDNA, Complementary DNA or RNA, DNA polymorphism, DNA sequencing, Double-stranded complementary DNA, Duplex DNA, Z-DNA.)

The use of DNA polymorphisms to detect the presence of a disease gene.

The unique pattern of DNA fragments identified by Southern hybridization (using a probe that binds to a polymorphic region of DNA) or by polymerase chain reaction (using primers flanking the polymorphic region).

See Ligase.

See Polymerase.

One of two or more alternate forms (alleles) of a chromosomal locus that differ in nucleotide sequence or have variable numbers of repeated nucleotide units. (See Allele.)

Procedures for determining the nucleotide sequence of a DNA fragment.

See Nuclease.

An allele is said to be dominant if it expresses its phenotype even in the presence of a recessive allele. See Allele, Phenotype, Recessive.

A gene whose phenotype is when it is present in a single copy.

A gene that stimulates cell proliferation and contributes to oncogenesis when present in a single copy. (See Oncogene.)

A period in which a plant does not grow, awaiting necessary environmental conditions such as temperature, moisture, nutrient availability.

Describes the coiling of the antiparallel strands of the DNA molecule, resembling a spiral staircase in which the paired bases form the steps and the sugar-phosphate backbones form the rails.

A duplex DNA molecule copied from a cDNA template.

The region extending in a 3' direction from a gene.

See double-stranded complementary DNA.

Double-stranded DNA.