The time is now. Sixty-one years ago, Watson and Crick published their one-page paper on the structure of DNA deoxyribonucleic acid with possible biological implications Watson and Crick, The DNA preparation that was used by Rosalind Franklin for her x-ray crystallography studies was prepared by a young dentist named Norman Simmons. Thirty-nine years ago, I attended the Recombinant DNA Workshop held at Asilomar, California, when practical guidelines were established, recommended, and adopted by the international community.
During the early years of the HGP , it took many months to years to complete a single human genome at a cost of millions of dollars. Meanwhile, Federal investments were being made in bioinformatics, instrumentation, and equipment for high-throughput nucleic acid sequencing to accelerate the speed and lower the cost of whole-genome sequencing.
In , individual genome sequences with annotations were completed for J. This heralded the beginning of literally personalized health care.
We now know that the amount of genetic variation between any two unrelated people is one base or nucleotide A, adenosine; T, thymidine; C, cytosine; and G, guanosine per thousand bases, or 0. Each person possesses variations in about 3 million bases out of the total 3 billion bases that comprise the human genome.
Information from each of our genome sequences, such as single-nucleotide polymorphisms SNPs , is now used to understand how DNA variations within our genome can affect our health Kornman and Duff, Another key consideration to explain genomic variation is called copy number variants CNVs. There are at least 1, CNVs—segments of chromosomes that are duplicated or lost in different people—and these are scattered around the human genome. We are now at the beginning of a new era of using genomic information to make critical healthcare decisions for personalized dentistry and medicine Collins, ; Feero et al.
Historically, genetics is the study of heredity, the process in which a parent passes certain genes on to their children. Additional characteristics or phenotypes affected by heredity or spontaneous genetic mutations include metabolism, mental abilities, natural talents, and susceptibility or resistance to certain diseases or disorders.
Once the HGP was completed in , a much clearer understanding of the human genome emerged. Adult humans have ten trillion somatic cells, each containing 46 chromosomes [2 sex chromosomes and 22 pairs of autosomal chromosomes named according to their size, 1 being largest and 22 the smallest ]. There are 21, functional genes and 19, pseudogenes in the human genome within the nucleus of every somatic cell in the body. Genes are sections of DNA, and the location of a gene is called the gene locus. Most functional genes encode information within exons, separated by introns, to make proteins.
RNA Is About to Make Personalized Medicine a Reality
Each gene has an upstream enhancer and promoter sequence as well as a terminal stop sequence. Each gene can produce more than one protein through a process called alternative splicing. More than 60 hereditary disorders are known to result from changes mutations in mitDNA associated with a number of phenotypes such as blindness, hearing loss, short stature, and metabolic disturbances. The vast majority of human diseases and disorders are polygenic and reflect many gene-gene and gene-environment interactions coupled with epigenetic gene modifiers.
Curiously, we know that monozygotic twins share a common genotype. Do they share a common phenotype? Recently, several studies have determined that monozygotic twins present phenotypic discordance, such as differences in susceptibilities to disease as well as a wide range of anthropomorphic features. Whereas monozygotic twins are epigenetically indistinguishable during the early years of life, older twins exhibit significant differences in the distribution of 5-methylcytosine DNA and histone acetylation, thereby affecting their gene expression portrait.
Succinctly, many newer studies now provide evidence for an appreciation of epigenetics toward understanding different phenotypes that can originate from the same genotype. Yet another dimension of genomics is that of inherited as well as acquired mutations such as found in various cancers.
Multiple endocrine neoplasia type 2 MEN 2 is an example of an autosomal-dominant hereditary cancer syndrome caused by missense gain-of-function mutations of the RET proto-oncogene and presents strong genotype-phenotype correlations Frank-Raue and Frank-Raue, Environmental insults from carcinogens or mutagens, such as found in tobacco products and benzene, are examples of acquired mutations during the lifespan that cause neoplasia as presented in oral and pharyngeal cancers. Several different gene mutations associated with the regulation of the cell cycle and intracellular signaling networks cause various cancers.
Genome-wide sequencing of DNA samples from patient lesion biopsy can rapidly inform oncology diagnosis and treatment strategies for chemotherapy McDermott et al. Three examples are selected to highlight the introduction of personalized medicine and dentistry.
- Immortal Sherwood!
- A Rose For Every Month.
- Traveling in England For Women (Travel Dining For Single Women Book 1).
More than half a century after the discovery of the molecular basis of sickle cell disease, the causes or explanations of the phenotypic heterogeneity of the disease are just becoming clear. Sickle cell disease is a genetic disorder in which the beta-chain of the human hemoglobin Hb gene is mutated, leading to an abnormal Hb. This mutation causes red blood cells RBCs to acquire a sickle shape under conditions of hypoxia, resulting in an array of phenotypes such as anemia, cell adhesion, vaso-occlusion, severe pain, stroke, and organ failure.
The genetic mutation is caused by a single amino acid substitution of glutamic acid replaced by valine at the sixth position of the beta-globin chain. Recent studies using SNP genotyping in patients with various phenotypes have discovered significant involvements of SNPs of different genes other than the beta-globin chain Driss et al. Diabetes is a chronic disease defined by hyperglycemia. The disease phenotype is heterogeneous and can be divided into subtypes depending on the underlying genetic cause s.
The common forms of diabetes—type 1 diabetes TIDM and type 2 diabetes T2DM —present significant genetic underpinnings but without a clear pattern of inheritance Hornstein and Shuldiner, The disease phenotypes are produced from interactions among multiple gene variants with environmental factors. Therefore, performing genetic studies in multiple human populations can identify disease risk alleles that are common in one population but extremely rare in others.
This approach has the potential to illuminate pathophysiology, health disparities, and the population genetic origins of disease alleles. A recent study discovered that sequence variants in the SLC16A11 allele are common risk factors for type 2 diabetes in Mexico but extremely rare in European and African populations Williams et al. SLC16A11 gene products alter lipid metabolism and produce intracellular increases in triacylglycerol metabolism Williams et al. Curiously, poorly controlled diabetes patients i. This disease results in a significant loss of connective tissue and bone loss associated with tooth loss in adults.
In addition to the various micro-organisms that constitute the biofilm, genetic and environmental factors, especially tobacco use, contribute to this disease. Genetic, dermatological, hematological, granulomatous, immunosuppressive, and neoplastic disorders are each associated with periodontal manifestations Pihlstrom et al. I found the book well written and a valuable source of information on and This book should be titled 'The new companies that want to sequence your genome', because unfortunately that's what it's mostly about.
Davies touches on all of the interesting technologies Kevin Davies, Ph. His previous book Cracking the Genome was translated into 15 languages. He was the founding editor of Nature Genetics , the world's leading genetics journal, which he headed for its first five years.
Davies holds an M. D in molecular genetics from the University of London. Will you be pressured, by insurance companies or by your employer, to get your genome sequenced? What psychological toll might there be to discovering you are at risk for certain diseases like Alzheimer's? And will the government or the medical establishment come between you and your genome?
Also in This Series.
More than Moore’s Mores: Computers, Genomics, and the Embrace of Innovation | SpringerLink
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