El Proyecto Genoma Humano

De Wikillerato

En 1990 el Departamento de Energía y el Instituto Nacional de la Salud de los E.E.U.U comenzaron el ambicioso proyecto de identificar los aproximadamente 25.000 genes que posee el genoma de los humanos. El trabajo se completó en el año 2003, aunque todavía en la actualidad se sigue analizando la gran cantidad de datos que generó. Las primeras impresiones

   * The human genome contains 3.2 billion chemical nucleotide bases (A, C, T, and G).
   * The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million base pairs.
   * Functions are unknown for more than 50% of discovered genes.
   * The human genome sequence is almost (99.9%) exactly the same in all people.
   * About 2% of the genome encodes instructions for the synthesis of proteins.
   * Repeat sequences that do not code for proteins make up at least 50% of the human genome.
   * Repeat sequences are thought to have no direct functions, but they shed light on chromosome structure and dynamics. Over time, these repeats reshape the genome by rearranging it, thereby creating entirely new genes or modifying and reshuffling existing genes.
   * The human genome has a much greater portion (50%) of repeat sequences than the mustard weed (11%), the worm (7%), and the fly (3%).
   * Over 40% of the predicted human proteins share similarity with fruit-fly or worm proteins.
   * Genes appear to be concentrated in random areas along the genome, with vast expanses of noncoding DNA between.
   * Chromosome 1 (the largest human chromosome) has the most genes (3168), and the Y chromosome has the fewest (344).
   * Particular gene sequences have been associated with numerous diseases and disorders, including breast cancer, muscle disease, deafness, and blindness.
   * Scientists have identified millions of locations where single-base DNA differences occur in humans. This information promises to revolutionize the processes of finding DNA sequences associated with such common diseases as cardiovascular disease, diabetes, arthritis, and cancers.

Organism Genome Size (Base Pairs) Estimated Genes Human (Homo sapiens) 3.2 billion 25,000 Laboratory mouse (M. musculus) 2.6 billion 25,000 Mustard weed (A. thaliana) 100 million 25,000 Roundworm (C. elegans) 97 million 19,000 Fruit fly (D. melanogaster) 137 million 13,000 Yeast (S. cerevisiae) 12.1 million 6,000 Bacterium (E. coli) 4.6 million 3,200 Human immunodeficiency virus (HIV) 9700 9

The estimated number of human genes is only one-third as great as previously thought, although the numbers may be revised as more computational and experimental analyses are performed.

Scientists suggest that the genetic key to human complexity lies not in gene number but in how gene parts are used to build different products in a process called alternative splicing. Other underlying reasons for greater complexity are the thousands of chemical modifications made to proteins and the repertoire of regulatory mechanisms controlling these processes.