The human genome map, probably the most significant scientific landmark in history, will revolutionize medical practice and biological research. The world community is sharing it’s research information over the Internet.
Eventually all human genes will be found, and accurate diagnostics for most inherited diseases will follow, advancing the understanding of the human genome for health and disease prevention.
The Human Genome Project’s primary goal is the assemblage of descriptive diagrams, maps of the human chromosome at increasingly finer resolutions. Determining the base sequence of each of the ordered fragments, finding all the genes and developing tools to assimilate this information will be the basis for vastly improved human biology and medicine.
Private companies spearheaded the innovative research, partly funded through government grants. Researchers are aided by the genetic studies of nonhuman organisms. These include the genomes of a common bacterium, the fruit fly, and the laboratory mouse. These simpler systems modeled the developing and testing procedures for studying the extraordinarily complex human genome.
Single genes, thus far, have been identified as responsible for cystic fibrosis, sickle cell anemia, duchenne muscular dystrophy, myotonic dystrophy, neurofibromatosis, and retinoblastoma. Other genetically susceptible disabling/fatal diseases include heart disease, stroke, diabetes, and some forms of cancer. The subtle abnormalities, or mutations, may predispose a person to cancer or major psychiatric illnesses.
Further study of the mechanisms for diseases caused by multiple genes and proteins will unmask effective therapies and preventive measures.
A brief description of the double helical structure and its components helps to better comprehend the enormity of this undertaking.
The human genome, found in every cell’s nucleus, consists of tightly coiled threads of DNA—deoxyribonucleic acid—and protein molecules, organized into structures called chromosomes. The strands of DNA, if laid flat and strung together, would extend more than five feet but are only a 50,000 billionth of an inch wide.
The DNA molecule of humans consists of two strands wrapped around each other resembling a twisted ladder. The sides are connected by rungs called bases. Each strand is a linear arrangement of chemicals. The particular order is called the DNA sequence, the exact genetic instructions required to create an organism with its unique traits.
The human DNA contains 23 pairs of chromosomes; the last identifies gender. The first human chromosome to be sequenced was in December 1999.
Down’s syndrome is a major chromosomal abnormality in which an individual’s cells contain a third copy of chromosome 21. Identifying other more subtle irregularities to the structure and sequence requires molecular analysis.
Disease occurs when proteins are produced incorrectly. It’s a job about 1,000 times more complicated than decoding the human genome, a task that cost the government-funded Human Genome Project 13 years and $2,530M, so far.
Much of the genome map will be superfluous,” said Bill Haseltine, president and CEO of Human Genome Sciences, “because 97% of the human genome contains no genes. The biologically important, protein-encoding sequence of genes are fragmented and dispersed, like so many pieces, needles in an enormous DNA haystack.”
Between these gene sequences, are vast structures with no coding and whose functions are not yet understood. Geneticists have so far charted the approximate positions of only 2.3% of the know genes.
DNA molecules are among the largest. Chromosomes can be seen under a simple light microscope. Stained with certain dyes, patterns of light and dark bands reveal the amounts of A , T, G and C chemicals. They can be distinguished from each other by size and banding pattern, an analysis called a karyotype.
The size of the genome is the number of base pairs that hold together the two DNA strands, one from each parent. In humans, this number is approximately 3,000 million.
Genes are the basic physical and functional units of heredity. A gene is a specific sequence of bases, the required instructions for constructing proteins. Proteins and enzymes for essential biochemical reactions, are the structural components of cells and tissues.
All living organisms are composed largely of proteins. Proteins are large, complex molecules with long chains of subunits called amino acids. Proteins contain twenty types of amino acids. Humans can synthesize 100,000 different kinds of proteins.
With a sample of a patient’s blood, qualified technicians will be able to identify the activity of the proteins and thus predict disease with complete accuracy.
While human genome research itself does not pose any new ethical dilemmas,
the potential misuse of the data does invite concern. Genome research projects
will ultimately improve the genomes of economically important farm animals and
crops.