Page 22 - Genetics_From_Genes_to_Genomes_6th_FULL_Part3

PART III Analysis of Genetic Information
9

chapter

Digital Analysis

of DNA

In 1989, when an episode of Star Trek: The Next Generation featured
this shot of DNA sequences on an imaginary computer screen, the
ability to sequence the human genome appeared to be a distant
dream in the realm of science fiction. Amazingly, the Human
Genome Project, which began the following year, achieved this
goal less than 15 years later.
© CBS Photo Archive/Getty Images
SINCE THE MID-NINETEENTH CENTURY, three advances
have transformed the field of genetics radically: Mendel’s chapter outline
discovery of fundamental principles in the 1860s, Watson
and Crick’s elucidation of DNA structure in 1953, and • 9.1 Fragmenting DNA
the Human Genome Project from 1990 to the present. In • 9.2 Cloning DNA Fragments
this chapter and the next, we discuss the Human Genome • 9.3 Sequencing DNA
Project and the field of genomics (the study of genomes) • 9.4 Sequencing Genomes
that it spawned.
The Human Genome Project was initiated to se-
quence and analyze the human genome in conjunction
with the genomes of several model organisms. A genome is the total digital informa-
tion contained within the DNA sequences of an organism’s chromosomes. The haploid
human genome contains a total of approximately 3 billion nucleotide pairs.
Prior to the inception of the Human Genome Project, the genome’s enormous size
caused many biologists to regard the objective of sequencing it as science fiction
achievable only in the distant future. Nonetheless, some scientists could foresee the
emergence of very fast and reliable automated (high-throughput) DNA sequencing
methods as well as the computational tools necessary for capturing, storing, and ana-
lyzing the vast amounts of data involved. Persuaded by these arguments, agencies of
the United States government agreed in 1990 to commit $3 billion over a projected
15-year period toward completion of the human genome sequence. Several interna-
tional organizations also joined the enterprise.
Remarkably, investigators were able to determine a rough sequence of the human
genome by February 2001. In this draft, the sequence had some gaps and did not yet
have an appropriate level of accuracy (an error rate of 1/10,000 or less). An accurate
sequence covering 97% of the genome was completed shortly thereafter in 2003, two
years ahead of schedule. The early finish was prodded by the 1998 promise of Celera,
a private company, to complete a draft of the genome in just three years at much lower
cost, employing a novel sequencing strategy. The internationally supported genome
effort reacted by moving its timetable ahead by several years.

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