The Human Genome Project

  1: What is the public project for sequencing the human genome?
  2: Has the human genome been completely sequenced?
  3: How many genes do humans have?
  4: Why is it so difficult to find the genes in a human genome sequence?
  5: Where did the sequenced human DNA come from?
  6: Is the human genome “freely available”? If not, who owns it?
  7: Why was there a Human Genome Project What is its use?
  8: Who were the members of the international consortium What was the role of each of them?
  9: What was the French contribution to the Human Genome Project?
  10: How much did the Human Genome Project cost?
  11: With the end of the Human Genome Project, are the large sequencing centers still useful?

  If you feel like going through the three billion letters which constitute the sequence of the human genome, you will have a hard time finding the parts which correspond to the instructions, or genes, in the monotonous succession of A, T, C and G nucleotides. No obvious characteristic makes a gene evident to the naked eye. And there are not many chances that a reading starting at a random location in the genome will lead you to a gene rapidly: in humans as in other mammals, the genes occupy less than 30% of the genomic DNA. Furthermore, the genes are fragmented: in plants and animals the biologically significant part of the genes is divided into blocks called exons, separated by intervening sequences called introns. Moreover, the exons represent less than 3% of the human genome and are not easy to delimit. For example, the 24 exons of the gene which encodes neurexin-3 are separated by very long introns, and are dispersed over about 1.5 million nucleotides on human chromosome 14!

A computer, however, can read the sequence of the human genome much more easily than the human eye. The study of the characteristics statistically associated with genes has led to computer programs for gene-finding, which are useful for large-scale preliminary annotation. These programs may make false predictions about the limits of an exon, however, or may miss an existing exon. They must therefore be complemented by an approach which uses experimental data. This approach consists in looking for similarities between the human genome sequence and various types of sequences, for example sequences of expressed gene products (messenger RNA and proteins), for which a large quantity of data has been collected in humans and other organisms beginning in the 1990s; and also genomic sequences which may come from human or other genomes. In the first example, the sequence of a gene is delimited by alignment with the sequence of its own messenger RNA, or the messenger RNA of a related gene; in the case of comparisons between genomic sequences the genes are identified on the basis of their “coding” parts, which have been more conserved during the course of evolution than the rest of the genome sequence. Genoscope uses conserved regions between the genomes of humans and that of a small fish, Tetraodon nigroviridis to improve the prediction of human genes.