DNA and use the single strands as templates for building new double-stranded DNA.

proteins:

molecules made up of long chains of amino acids. They build tissues and carry out many critical functions in the body. Proteins literally make us what we are.

recombinant DNA:

novel DNA made by joining DNA fragments from different sources.

restriction endonuclease (or enzyme):

an enzyme that cuts a DNA molecule at a particular base sequence.

Restriction Fragment Length Polymorphism (RFLP):

the variation, within a population, of the lengths of restriction fragments formed by treating DNA with a restriction enzyme. Responsible for the difference in DNA fingerprints of individuals.

retrovirus:

virus having RNA as the genetic material. Inside the infected host cell, the viral RNA is used as a template for making viral DNA, which then becomes integrated into the host cell's chromosomal DNA. From there, the viral DNA can direct the formation of more, identical viruses.

reverse transcriptase:

a retroviral enzyme that uses RNA as a template for making DNA.

ribonucleic acid (RNA):

A nucleotide chain that differs from DNA in having the sugar ribose instead of deoxyribose, and having the base uracil instead of thymine. RNA helps translate the instructions encoded in DNA to build proteins.

transgenic organism:

an organism into which the genes of other species have been engineered.

vector:

in genetic engineering, an entity used to carry recombinant DNA into a cell. Plasmids and phages are commonly used as vectors.