Over the past 20 years, the field of biology has experienced a phenomenal series of advancements pertaining to genomic sequencing. Today, the scientific community has generated large databases of genomic sequences. Genomic sequencing has advanced to a stage where biotechnology companies are thriving, allowing a previously complex and expensive procedure to be commercialized and accessible to the public.
DNA is comprised of four nucleotides, each with a corresponding shorthand letter name that is widely recognized in science – Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). DNA is commonly said to contain all the information that is required for life – that is, the body can interpret the linear order of DNA, and translate it into proteins that carry out the functions required for life. Each nucleus in human cells contains approximately 6 billion base pairs worth of DNA.
Sequencing the genome refers to the process of finding the order of nucleotides that are within a person’s cells. However, finding the sequence can allow biologists to elucidate far more about DNA. Having the sequence allows for the maps for locations of genes to be extrapolated. It also allows the creation of linkage maps, to be traced over generations.
Genomic sequencing first began in the 1970s. The proposal for the Human Genome Project (HGP) was first articulated in 1988. The project was an immense, international collaborative research project that has been deemed the “culmination of history of genetics research”. The primary goal of the HGP was to sequence the entire human genome. This effort included the help of 20 elite genomic institutions across six countries.
By 2001, 90% of the human genome was sequenced for the first time in human history. The project was long and intensive. The first portion of it involved mapping the human genome. This generated a reference sequence, with a low estimated error of 1 in approximately 10000 base pairs. The reference sequence is analogous to a “draft”. The mapping phase of the project costed at least tens of millions of dollars. In reality, it likely cost hundreds of millions.
The enormous length of the human genome prevents it from being sequenced in one read. Instead, current methods involve a technique called shotgun sequencing. The DNA is broken up into shorter fragments. Each fragment is then sequenced, and computational methods are used to piece the entire genome together. Through this method, the entire genome was published in 2003. The Human Genome Project was completed ahead of schedule and under budget.
In 2006, the cost to sequence an individual’s entire genome was estimated to be $20 million. Since then, companies have begun developing faster and cheaper methods of sequencing, known as “next-generation sequencing”. From mid-late 2015, the cost of generating a draft dropped from $4000 to $1500. Currently, the human genome can be sequenced for under $1000. Illumina, a leading frontier in the commercialized field of genomic sequencing, is hoping to be able to sequence the genome for under $100.
Genome sequencing allows us to determine differences or abnormalities in a person’s genomic composition. Scientists can now compare mutations with the expected sequence. It will be possible to find single nucleotide polymorphisms and identify translocations. It also allows scientists to characterize the functions of genes, such as seeing the difference between coding and non-coding regions. It allows study on epigenetics, a growing field that analyzes the chemical modifications that are made on genes. These modifications, including but not limited to phosphorylation and methylation, have been shown to be critical for cells to regulate gene expression.
The study can be used to understand aberrant phenotypes that arise in disease, since we will be able to better understand growth, development, and disease progression. In the near future, people will be able to sequence their genome as part of medical procedures.
Sequencing the genome greatly expands the capabilities of understanding the genomic code and enables advancements in the medical field. Its applications are widespread throughout different areas of biology, and continues to show great potential and merit in genetics research.