• Home
  • Sitemap

Chapter 5 Genomic diagnostics


1.Genomic tests and diagnostics

As described earlier, our genome has particular sequences which are inherited from our parents - namely," the constitution" (the original nature of our body).

For example, the relations between "metabolic syndrome" and "obesity" have been studied extensively. As a result, many symptoms which appeared in the metabolic syndrome are considered mainly due to the accumulation of visceral (intra-abdominal) fat.

The human beings had experienced continuous starvation during the long history of evolution, and had acquired a system which can store energy as visceral fat. After acquisition of the system, human beings could eat as much as he could whenever he found the food, and energy was stored inside of abdomen as fat.

However, in the modern life style in advanced counties, we can easily obtain food as we want. In the era of abundance, this wonderful system of storing the energy within our body that our ancestors had acquired, becomes disadvantageous and even unnecessary to us, since the system induces a new disease of "metabolic syndrome" due to excess accumulation of the abdominal fat.

In addition, many genetic mutations occurred during the long period of human evolution stage. Today, human beings have inherited these genetic mutations from our ancestors which created many different genomic types. In the case of obesity related genomic types, it has been known that the resting metabolic rate (RMR, the minimum required energy for each individual) can be different according to the difference in the genome type.

For instance, a person having a specific genome type could have a tendency of obesity even though the person is trying to reduce the food intake. On the contrary, other person having another specific genome type could have little tendency of obesity, even the person is eating a lot. Therefore, it is necessary to find out the genomic type for the diet control of the person having metabolic syndrome, in order to understand the genetic characteristics and make the most suitable personal therapy.

Recently, it becomes necessary to find out the genome type of each individual, in order to understand the nature of our body. An individual diagnostic and medical treatment should be carried out based on these findings. In general, the procedure to find out the individual genomic information including genomic type and sequence, is called "genomic test", and a diagnostic based on the genomic test is called "genomic diagnostic".

Genomic tests have been widely used not only for the metabolic syndrome, but also for genetic diseases, forensic examinations, infectious diseases, identification of parents and children, etc. One of the typical examples of the genomic diagnostic is a new type of influenza which widely spread in the world in 2009. In this case, the new type influenza has a specific genomic sequence which is found by the genomic test.


2.Examples of the genomic test

In general, there are three categories among the genomic test:

  • 1 Examination of individual genomic sequence and specific genome type
  • 2 Detection and identification of foreign infectious species
  • 3 Examination of genomic sequences of plant and animal

Among these, in case of the examination of individual genome type or genomic sequence, the results of examination must be kept under strict protection. In addition, when the examination is carried out, it is necessary to explain to the individual the contents of examination and obtain sufficient informed consent. A typical example is the examination of particular inherited genetic disease which is caused by certain genomic abnormalities such as mutation, defect of gene, or existence of the specific genome sequence. The test is needed to assess the possibility of causing a particular genetic disease.

An example of the case (2) is an examination of AIDS caused by HIV virus.

In this case, it is absolutely necessary to protect the individual information which is obtained by the results of the examination. Also, the sufficient informed consent before the examination must be received. In general, the genomic examination on human beings is not only concerned with technical issue, but also with ethical issue and social view points. Thus, a very careful handling of the overall procedure is absolutely required.

An example of the case (3) is an examination of gene-engineered plant products like corn, soy beans, rice etc. For example, a large amount of soy beans are consumed in Japan as the raw material for tofu, soy source, etc., and the genomic examination has been carried out to meet demand.


3.How the genomic examination is performed?

In general, a typical genomic examination consists of the three processes as follows:

In the case of human genomic examination, samples are collected as either humor (blood, saliva, urine etc.) or tissues (nail, hair, organ tissue etc.). The first treatment for the sample is the extraction/ purification of DNA.

In the past, this procedure has been carried out manually, but in recent years, a fully automated system has been developed, which allows the extraction/purification procedure to be much more efficient than before.

The next process is DNA amplification, because the amount of extracted DNA is usually not enough to the analysis. In this process, PCR method (The Polymerase Chain Reaction) has been widely used. PCR method is also possible to amplify the necessary fragment of genomes from the long chain human DNA.

The last step is the analysis of the amplified DNA. In general, the fluorescence-labeled DNA has been used for the detection by the optical measurement.

A fully automated instrument for each step has been developed and widely used. Recently, the integrated system combining these steps has been also developed.

  • BACK
  • NEXT
  • Chapter 1 Genome and our body
  • Chapter 2 Gene expression and protein synthesis
  • Chapter 3 Mechanism of gene expression
  • Chapter 4 Genome type
  • Chapter 5 Genomic diagnostics
  • Chapter 6 Personalized medicine