Number: of human genes

Many important findings have already emerged. The one to date that has generated the most discussion is that the number of human genes may be only two to three times that estimated for the roundworm and the fruit fly. 

The phenomenon of imprinting refers to the fact that a small number of human genes are transcriptionally active only when transmitted by one of the two sexes. A good example is provided by Prader-Willi syndrome, a disorder characterized by moderate mental retardation, hypogonadism, small hands and feet, and obesity. Most cases of Prader-Willi syndrome are caused by a deletion of 4 million bases (4 megabases or Mb) on the long arm of chromosome 15. However, the deletion produces this syndrome only if it is transmitted by the fether. If the same deletion is... 

After completion of the human genome sequence with the reduced estimation of the number of human genes the focus has now switched to proteomic strategies. Future studies will focus on the pain-associated modification or translocation of pain-relevant proteins, and will elucidate signaling mechanisms by identifying protein-protein interactions. 

I am confident that with the approach of the postgenome era, an ever-increasing number of human genes will be discovered and their functions elucidated. Combined with the knowledge of human gene polymorphism, genotyping will allow prediction of the genetic predisposition to certain diseases, such as cancer. The new millennium will usher us in a new era of disease-predictive medicine. 

The number of human genes was recently estimated as 30,000 rather than the previously estimated number of 100,000, still believed by other experts. Francis S. Collins, Director of the National Human Genome Research Institute, commented that the complexity of how proteins function in humans probably accounts for the difference. If this functional complexity is the result of protein modifications, MS will play a vital role in determining the position and type of modification (e.g., phosphorylation, liposylation, and glycosylation). 

Transgenic animal models with spontaneous or induced receptor gene defects have been instrumental in elucidating the physiological roles of the LDL receptor gene family. In addition, a number of human diseases have been identified that are caused by sporadic or inherited forms of receptor deficiency (Table 1). 

Potentially, interferon is an ideal anhviral agent in that it acts on many different vimses and is not toxic to host cells. However, the exploitation of this agent in the treatment of viral infechons has been delayed by a number of factors. For example, it has proved to be species-specific and interferons raised in animal sources offered little protechon to human cells. Human interferon is thus needed for the treatment of human infechons and the produehon and purificahon of human interferon on a large scale has proved difficult. The inserhon of human genes for interferon into E. coli has resolved the produehon problems (Chapter 24). Clinical trials have demonstrated that interferon prevents rhinovirus infeehon and has a beneficial effect in herpes, cytomegalovims and hepahtis B vims infechons. 

Roest Croellius H et al. Estimate of human gene number provided by genomewide analysis using Tetradon nigroviridis DNA sequence. Nature Genet 2000 25 235-238. 

Mutations associated with inheritable diseases are numbered in MIM notation as described in McKusick, V. A. Mendelian Inheritance in Man. A Catalog of Human Genes and Genetic Disorders, 12th edn. Baltimore Johns Hopkins University Press, 1998. An updated Internet version is found at Online Mendelian Inheritance in Man, OMIM . McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD), 2000, www.ncbi.nlm.nih.gov/ omim/. 

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