Sequencing

  1: What is the DNA sequence?
  2: Why do we sequence DNA?
  3: How do we sequence DNA?
  4: What is the assembly?
  5: Why were Genome Centers created?

To understand the instructions “encoded” in a DNA molecule, one must start by determining the sequence of its bases. It is this “reading” of the sequence which is called sequencing. In contrast to reading a text, which gives immediate access to the comprehension of the message, the sequencing of DNA only provides a long succession of A,T, G and C in which the instructions are not immediately comprehensible. An interpretation step, called annotation, is therefore necessary to (1) identify the instructions and (2) understand the biological sense.

The constitution of an exhaustive inventory of the instructions, or genes which are contained in the genome, is the principal reason for the sequencing programmes. A knowledge of the genes is an indispensable step in the comprehension of biological phenomena at the molecular and cellular level. In the coming years, applications will be more and more numerous in the domains of medicine, the pharmaceutical industry, biotechnology, and agri-business, as well as in other fields which are directly dependent on biological processes (agriculture, environment). For all of these applications, the sequence is the starting point. (See also “Large sequencing centers—are they still useful?”) List of questions.