alkaptonuria:

a genetic disease in which the urine turns black when exposed to air, due to homogentistic acid in the urine.

amino acids:

naturally occurring biological molecules with a variety of functions. Among the amino acids, there are 20 that are used as building blocks for making proteins.

antisense therapy:

administration of a drug consisting of short pieces of artificially produced, single-stranded DNA (about 15 to 25 nucleotides). The DNA is complementary to a section of an RNA molecule. It base-pairs with the RNA and prevents it from making a protein that is harmful to the system.

Bacillus thuringiensis:

a strain of bacteria that produces a protein toxic to certain insects that cause significant crop damage. The bacteria are often used for biological pest control. Recently, the gene that codes for the toxic protein has been engineered into other soil bacteria and also directly into some crop plants.

bacteria:

one of the five kingdoms of living things. Bacteria are structurally simple single cells with no nucleus.

bacteriophage (or phage):

a virus that infects bacteria. They are used by genetic engineers to introduce genes into bacterial cells.

base:

one of the building blocks of DNA or RNA. A nitrogen-containing base combines with sugar and phosphate molecules to make a nucleotide. The four bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).

base pair:

two nucleotides held together by a weak bond between complementary bases. In DNA molecules, adenine is paired with thymine and guanine is paired with cytosine.

cells:

the basic structural units of life.