2.3. A Genomic View of Life
pp. 21-23 in
Bioethics and the Impact of Human Genome Research in the 21st Century
Author: Yuji Kobara (DNA Research Centre, National Institute of Genetics, Japan)Editors: Norio Fujiki, Masakatu Sudo, and Darryl R. J. Macer
Eubios Ethics Institute
Copyright 2001, Eubios Ethics Institute
All commercial rights reserved. This publication may be reproduced for limited educational or academic use, however please enquire with the author.
2.3. A Genomic View of Life
The impact of the recent output of genome analysis is enormous. The genomic sequencing of dozens of microorganisms showed that the genome structure has changed dynamically among species, leading to rethinking of the definition of a species in microorganisms. The genome sequencing of nematode, fruit fly, Arabidopsis and humans is providing clues to the understanding of the 'strategy of life' in evolutionary history. I believe that the consideration of evolutionary aspects of the genome is essential for understanding of ourselves.
l) The gene number in the genome
Evolution through gene duplication produced multicellular organisms, and also produced vertebrates through genome duplication (at least twice). The gene numbers of prokaryote and lower eukaryote genomes are around 1000 to 4000 and about 7000, respectively, while that of invertebrates like nematode and fly increase, to IOOO0-20000. The gene number of the human genome is estimated to be around 30000, which roughly corresponds to double that of invertebrates. These facts mean that the genome of invertebrates is the prototype of the human genome. and suggest that the gene number of vertebrates is essentially the same from fish to humans.
2) Diversity in the manner of gene utilization
It was surprising that the genes in fly genome were less than (at least. no more than) those in nematode, since fly is obviously more complex than nematode. It is much more surprising that fish and human genomes have the similar gene number. How does 'life' manage to generate different species from a similar set of genes? The following mechanisms could work for generating the diversity in gene expression, including altemative splicing. difference in expression patterns (spatial and temporal) imprinting and genome rearrangements in somatic cells.
The genomes of human and chimpanzee are estimated to be 98% plus identical. If so, what causes the difference between monkey and ourselves? The knowledge of the differences between the genomes should provide the clues to the mechanisms of humanization.
3) Genome diversity among individuals
The human genome is polymorphic (1 SNP/1000 bases). This diversity eventually directs a wide range of human characters including susceptibility to diseases, physical constitution and various abilities. It is estimated that the degree of genome diversity is greater between individuals than between races. This means that our characters are not completely determined but largely acquired, and that the potentiality of our abilities is enormous. I believe that the genome diversity is essential to our future.
Figure 1: History of DNA Sequencing
Figure 2: Progress in DNA Sequencing and Related Technology
Figure 3: Biohistory
Figure 4: Evolution of the Genome
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