Eukaryotes Genomes - HOMO SAPIENS

Homo sapiens (Latin for knowing man), more commonly known as human beings, are defined variously in biological, spiritual, and cultural terms. Biologically, they are classified as a primate species of mammal with a highly developed brain. In cultural anthropology, they are defined by their use of language, their organisation in complex societies and their development of technology. From a scientific viewpoint, Homo sapiens is among the most generalised species on Earth. Smaller and simpler organisms such as bacteria and insects greatly surpass humans in population size and diversity of species, but few single species occupy as many diverse environments as humans.

Humans consider themselves the most intelligent organism in the animal kingdom. Humans have the highest brain to body mass ratio of all large animals. Various attempts have been made to identify a single behavioural characteristic that distinguishes humans from all other animals, e.g. the ability to make and use tools, the ability to alter the environment, language and the development of complex social structures. Considered in isolation, however, these differences are not absolute, as ethologists have recorded such behaviours in many species, for example Apes and even birds, are known to "fish" for insects using blades of grass or twigs, and even to shape the tools for that purpose. For these reasons, the idea that making and using tools is a defining characteristic of humans is often considered outdated. Similarly, other animals often have methods of communication but the degree to which humans create and use complex grammar and abstract concepts in language has not been seen in any other species. Some anthropologists think that these readily observable characteristics (tool-making and language) are based on less easily observable mental processes that might be unique among humans: the ability to think symbolically, in the abstract or logically, although several species have demonstrated some abilities in these areas.

The oldest fossil evidence for anatomically modern humans is about 130,000 years old in Africa, and there is evidence for modern humans in the Near East sometime before 90,000 years ago. The origin of modern Homo sapiens is not yet resolved. Two extreme scenarios have been proposed. According to the first, all modern humans evolved in parallel from earlier populations in Africa, Europe and Asia, with some genetic intermixing among these regions. Support for this comes from the similarity of certain minor anatomical structures in modern human populations and preceding populations of Homo erectus in the same regions. A different model proposes that a small, relatively isolated population of early humans evolved into modern Homo sapiens , and that this population succeeded in spreading across Africa, Europe, and Asia -- displacing and eventually replacing all other early human populations as they spread. In this scenario the variation among modern populations is a recent phenomenon. Part of the evidence to support this theory comes from molecular biology, especially studies of the diversity and mutation rate of nuclear DNA and mitochondrial DNA in living human cells. From these studies an approximate time of divergence from the common ancestor of all modern human populations can be calculated. This research has typically yielded dates around 200,000 years ago, too young for the "Multiregional Hypothesis." Molecular methods have also tended to point to an African origin for all modern humans, implying that the ancestral population of all living people migrated from Africa to other parts of the world, the name of this interpretation is the "Out of Africa Hypothesis"

In the 1980s, people such as Jim Watson , co-discoverer of the DNA double helix, proposed that sequencing all three billion letters of the human genetic code might be possible. They argued that the sequence would be an invaluable tool for biomedical research.

The human genome, the book of instructions needed to build a human being, is written in a four-letter DNA code . Although small genomes had been sequenced, the human genome was on a completely different scale. Many felt that it was a step too far, or would squeeze resources out of other areas of science. So in the meantime, mapping and sequencing continued on other smaller organisms.

The Wellcome Trust saw that a human genome sequence would be a force for accelerating biomedical research - one of the main aims of the Trust - and seized the opportunity to support the global Human Genome Project.

Jointly with the MRC, a centre dedicated to genome sequencing was established.The Hinxton Hall estate became available and existing laboratories there were quickly converted. By April 1993, 15 researchers were at work, and construction began on modernising an existing research building. The Sanger Institute, as it was then known, was formally opened by Fred Sanger in October 1993. The new facilities, added to over the following years, enabled the Sanger Institute to become one of the world's most productive genome sequencing centres.

Two Independent drafts of the human genome sequence were published simultaneously in February 2001.The human genome is by far the largest genome to be sequenced, and its size and complexity present many challenges for sequence assembly. The International Human Genome Sequencing Consortium constructed a map of the whole genome to enable the selection of clones for sequencing and for the accurate assembly of the genome sequence. The Wellcome Trust Sanger Institute made the largest single contribution to the human genome sequence

Only a decade ago, most scientists thought humans had about 100,000 genes. The finished human genome analysis suggests suggests that there are perhaps only 20,000-25,000 protein-coding genes in our human genome.

Information found from sequencing the human genome:

• It covers 99% of the gene-containing parts of the genome and is 99.999% accurate
• The new sequence correctly identifies almost all known genes (99.74%)
• It defines 22,287 'gene loci', consisting of 19,599 protein-coding genes in the human genome and another 2,188 DNA segments that are predicted to be protein-coding genes
• It identifies the 'birth' of 1183 genes in the last 60-100 million years
• It identifies the 'death' of 30 or so genes in a similar time period
• The accuracy and completeness allows systematic searches for the causes of disease, for example, to find all key heritable factors predisposing to diabetes or mutations underlying breast cancer - with confidence that little can escape detection
• At a practical level, it eliminates tedious confirmatory work by researchers, who can now rely on highly accurate information

References:

http://www.mnh.si.edu/anthro/humanorigins/ha/sap.htm
http://www.sanger.ac.uk/Info/Press/2004/041020.shtml
http://www.nature.com/genomics/human/
http://news.bbc.co.uk
http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html
http://www.pbs.org/wgbh/aso/databank/entries/do53dn.html
http://www.chemheritage.org/EducationalServices/chemach/ppb/cwwf.html
http://www.genome.gov/10005831
http://www.dnaftb.org/dnaftb/13/concept/
http://bioinfo.mbb.yale.edu/course/projects/final-4/
http://www.sanger.ac.uk/Info/Intro/sanger.shtml
http://www.sanger.ac.uk/HGP/publication2001/
http://www.yourgenome.org/timeline.html