DNA Sequencing – Whole-Exome and Whole-Genome Sequencing

DNA Sequencing

DNA Sequencing is the process of determining the order of nucleotides (building blocks) in an individual’s genetic code. This information helped us to know the type of genetic information carried in the DNA molecule that can be held responsible for body functions. In this way, genetic changes are detected which may cause certain health conditions.  DNA sequencing is one of the techniques for testing for genetic disorders.

DNA structure is in the form of a double helix and consists of four chemical bases. These nucleotides are adenine, cytosine, guanine, and thymine. These nucleotides occur in the pair like adenine make pair with thymine while guanine with cytosine. These pairs make DNA molecules.

DNA sequencing involves two methods

genetic changes

These are given below.

  1. whole-exome sequencing: This process of sequencing in which exome are sequenced is called exome sequencing
  2. whole genome sequencing: The process of sequencing in which genome is sequence is called genome sequencing

Both of these methods are used in the research and healthcare segment to identify genetic variants.

  1. The Next-generation Sequencing (NGS test)

Advancement in the above-mentioned two technologies has enabled rapid sequencing with a large amount of DNA. These advancements are incorporated in Next Generation Sequencing (NGS). The NGS is being used to diagnose different types of cancers especially nasopharyngeal cancer. This test can diagnose nasopharyngeal cancer in the early stages well before the sign appear. So, the doctor can ask the patient to take preventive measures and may start the treatment. Following are some benefits of this NGS test.

  1. The NGS can test multiple genes at the same time to know mutation or disease marker
  2. This test also helps to know previously unknown disease marker
  3. This test also gives some additional information that may help for different treatments

The original sequencing technology (Sanger sequencing) was a breakthrough in the healthcare segment and research because it enabled scientists to determine genetic code. This first sequencing technique but was expensive and time-consuming. Now in these days, the Sanger sequencing method is automated tomake it speedy and used in laboratories to sequence short strands of DNA but is very difficult to sequence all DNA of a person because it can take years.  That is why this first Sanger sequencing is replaced by the new next-generation sequencing. The NGS speeds up the process and the human genome is sequenced in days to weeks. This feature also reduces the cost.

Now with the help of next-generation sequencing, it is possible to sequence DNA. In other words, now it is possible to sequence all the pieces of DNA that provide instruction for protein in an individual. These pieces of DNA are called exons. These exons are thought to make one percent of the person’s genome.  So, all the exons together in the genome are called the exome. The process in which exome are sequenced is called whole-exome sequencing. Any variation in the protein-coding region in any gene are identified by whole-exome sequencing.  This is known before, that disease-causing mutations take place in the exome. That is why the whole-exome sequencing method is considered to be most effective in finding possible disease-causing mutations.

The researchers have also found gene activity and protein production are also affected by DNA variations outside the exome. This can also cause a genetic disorder. The whole-exome sequencing can miss identifying these variations. Another process that determines order of the nucleotides in individual’s DNA including variations in parts of the genome is called whole-genome sequencing.

You can identify multiple genetic changes within whole-exome sequencing and whole-genome sequencing in comparison with single-gene sequencing. It is also known that all genetic changes don’t affect health and it is very difficult to know either identified variants are responsible for causing the certain condition. It has also been in the knowledge of researchers that an identified variant is linked with different genetic disorders.

After careful analysis of the advantages and disadvantages of whole-exome sequencing and whole-genome sequencing, these techniques are helpful for researchers.

 Application of DNA Sequencing


DNA sequencing can be used in different fields. It is being used in the following fields.

  1. Biologic research
  2. Biotechnology
  3. Forensic biology
  4. Virology
  5. Medical diagnosis

Researchers are already using results of DNA sequences in comparison with long lengths of DNA. This information helping us to know about the following.

  1. The role of certain DNA patterns and susceptibility to the health condition.
  2. The role of certain DNA patterns and responses to medical treatment.

The extensive use of this sequencing technique will be more by the doctors and other healthcare professionals in the future but it is still being used in the diagnosis of some health conditions especially in the diagnosis of cancer of different types. In the future, the use of this sequencing technique will also be helping humans other than cancer segments like cardiovascular problems and diabetes.

Doctors usually ask to go for many tests to confirm a diagnosis or to rule out a condition. They also order different tests for differential diagnosis because many conditions have the same signs and symptoms. Some of the tests are used to know either treatment is working or there is a need for medicine doze adjustment. Different tests and techniques are used by medical science in the diagnosis of all types of cancer. The diagnosis of cancer becomes difficult when disease prevalence is also poor and confined to specific areas of the world. For example, nasopharyngeal carcinoma is not a common type of cancer. It has affected more people in China than people in other parts of the world. That is why there is more advancement in the diagnosis of this type of cancer in China. Take2 Health has taken steps to incorporate medical research and information technology for the betterment of human beings.  Efforts of taking 2 Health in starting NP blood tests like NGS are appreciable.

Article Submitted By Community Writer

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