Long-range restriction mapping
Restriction enzymes are proteins that cut DNA at precise locations. Restriction maps depict the positions on chromosomes of restriction enzyme cutting sites. These are used as biochemical "signposts", or markers of specific areas along the chromosomes. The map will detail the positions on the DNA molecule that are cut by particular restriction enzymes.

Cloning vector
A cloning vector is a DNA molecule (from a bacterium, virus, or yeast) that carries a piece of foreign DNA (which can be of any origin, including human) into a host cell (usually a bacterial or yeast cell). The foreign DNA will be reproduced when the host cell reproduces. Collections of these cells that stably maintain foreign DNA are called clone libraries. Stable clone libraries with large DNA inserts are crucial resources for genome researchers.

PCR (polymerase chain reaction)
PCR is a way researchers copy or "clone" a piece of DNA to obtain sufficient material for experiments. It does not require a host cell and is extremely fast, and sensitive.

Shotgun sequencing
This strategy involves randomly sequencing tiny cloned pieces of the genome, with no foreknowledge of where on a chromosome the piece originally came from. This can be contrasted with "directed" strategies, in which pieces of DNA from adjacent stretches of a chromosome are sequenced. Directed strategies eliminate the need for complex reassembly techniques. Because there are advantages to both strategies, researches expect to use both random (or shotgun) and directed strategies in combination to sequence the human genome.

Positional cloning
Positional cloning in a technique used to identify genes, usually those that are associated with diseases, based on their location on a chromosome. This is in contrast to the older, "functional cloning" technique that relies on some knowledge of a gene's protein product. For most diseases, researchers have no such knowledge.

Polymorphism
From the Greek meaning "many shapes," polymorphism in genetics means different DNA sequences. Polymorphisms can occur within protein-coding regions (genes) and noncoding regions. Researchers can trace these DNA differences through several generations to find disease genes and to construct detailed chromosome maps.

Gel electrophoresis
This is a technique that is very important in DNA sequencing. Standard sequencing procedures involve cloning DNA fragments into special sequencing cloning vectors that carry tiny pieces of DNA. The next step is to determine the base sequence of the tiny fragments by a special procedure that generates a series of even tinier DNA fragments that differ in size by only one base. These nested fragments are separated by gel electrophoresis, in which the DNA pieces are added to a gelatinous solution, and allowing the fragments to work their way down through the gel. Smaller pieces move faster and will reach the bottom first. Movement through the gel is hastened by applying an electric field to the gel.