Despite indispensable, the number of essential genes is composed to be the minority in an organism. In the single-celled Saccharomyces cerevisiae (yeast) genome, the whole genome systematic gene knockout analysis found 18.7% genes that are essential for viability (GIAEVER et al. 2002). There are around 25% in Drosophila (DIETZL et al. 2007). In Caenorhabditis elegans (C. elegans), it is estimated that there are ~15% of the total genes in the genome are essential genes (JOHNSEN AND BAILLIE 1997), although genome-wide gene knockdown analysis using RNA interference (RNAi) only successfully identified 7% (1,170 of 16,757) defective genes that result in sterility, embryonic or larval lethality (KAMATH et al. 2003), which, however, might miss some
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They can help to determine the minimal gene set, which is the smallest group of genes that are necessary and sufficient to sustain a functioning cell under the most favorable conditions (reviewed in KOONIN 2000). Thus, it will further our understanding of the basics of cell functioning. From a practical perspective, some essential genes that are conserved across all or most of the pathogenic bacteria but not in eukaryotes could become attractive candidates for broad-spectrum drug targets (reviewed in GALPERIN AND KOONIN 1999). In human, it has been demonstrated that mutations in essential genes contribute to a spectrum of human diseases, from developmental diseases leading to spontaneous abortions to different types of cancer, such as brain and breast cancer (DICKERSON et al. 2011). Knowing what are essential genes and how they work will allow researchers to understand the molecular nature of such …show more content…
elegans is very suitable for genetic study with its short life cycle, two sexes of both self-fertilizing hermaphrodites and males, and easy cultivation in the laboratory, which makes it easy for researcher to perform genetic crossing (BRENNER 1974). Second, although the adult hermaphrodite has only 959 somatic cells, it contains many different organs and tissues including muscle, hypodermis, intestine, reproductive system, and a nervous system with 302 neurons, which can also be found in high level eukaryotes (RIDDLE et al. 1997). Third, mutations in the genome can be induced by chemical mutagenesis, as a consequence, mutants with the discernable phenotypes can be easily isolated. Furthermore, as the first animal to have its genome completely sequenced, with a haploid DNA content of 100 million base pairs, the availability of the whole genome DNA sequence of C. elegans has brought many advantages on the studies in C. elegans. At last, the protein comparison between C. elegans and human showed that there is significant sequence similarity: 36% of 18,819 proteins in C. elegans were found to be orthologs to human proteins, while 74% of 4,979 proteins in human match to proteins in C. elegans (CONSORTIUM
They can help to determine the minimal gene set, which is the smallest group of genes that are necessary and sufficient to sustain a functioning cell under the most favorable conditions (reviewed in KOONIN 2000). Thus, it will further our understanding of the basics of cell functioning. From a practical perspective, some essential genes that are conserved across all or most of the pathogenic bacteria but not in eukaryotes could become attractive candidates for broad-spectrum drug targets (reviewed in GALPERIN AND KOONIN 1999). In human, it has been demonstrated that mutations in essential genes contribute to a spectrum of human diseases, from developmental diseases leading to spontaneous abortions to different types of cancer, such as brain and breast cancer (DICKERSON et al. 2011). Knowing what are essential genes and how they work will allow researchers to understand the molecular nature of such …show more content…
elegans is very suitable for genetic study with its short life cycle, two sexes of both self-fertilizing hermaphrodites and males, and easy cultivation in the laboratory, which makes it easy for researcher to perform genetic crossing (BRENNER 1974). Second, although the adult hermaphrodite has only 959 somatic cells, it contains many different organs and tissues including muscle, hypodermis, intestine, reproductive system, and a nervous system with 302 neurons, which can also be found in high level eukaryotes (RIDDLE et al. 1997). Third, mutations in the genome can be induced by chemical mutagenesis, as a consequence, mutants with the discernable phenotypes can be easily isolated. Furthermore, as the first animal to have its genome completely sequenced, with a haploid DNA content of 100 million base pairs, the availability of the whole genome DNA sequence of C. elegans has brought many advantages on the studies in C. elegans. At last, the protein comparison between C. elegans and human showed that there is significant sequence similarity: 36% of 18,819 proteins in C. elegans were found to be orthologs to human proteins, while 74% of 4,979 proteins in human match to proteins in C. elegans (CONSORTIUM