Entering Post Genome
Entering Post Genome: Single Nucleotide Polymorphism(SNP) and Microbiome
Human Genome Project and Post Genome
Human Genome Project(HGP) is the largest international biology research project. It defines the sequence of base pairs of DNA of the human genome. There are approximately 3 billion nucleotide base pairs in human genome. Since genome is a full set of genetic information of a single organism, the Human Genome Project is a significant discovery that is a ‘breakthrough’. It revealed many key findings of human genomics such as the number of genes listed in the human gene; it is to be around 22,500.
It is too difficult to sequence every single base pair of human genome, so the researcher used a shortcut. They first cut the DNA into small chunks (~150,000 bp) that has overlapping part at the ends. Then the chunks are copied in the ‘bacterial artificial chromosomes’. Now the researchers had to ligate the tiny pieces all together. As they wanted the missing parts to be as small as possible, the ‘hierarchical shotgun sequencing’ was selected, which is based on the Sanger sequencing. They broke the pieces into smaller fragments (~1000 bp) and ordered the fragments. This method is composed of two steps of fragmenting, and it makes their sequence assembly easier.
This huge project had influenced several important fields recently, especially health care. Nowadays people can understand the diseases deep into molecular level. In addition, the treatment of the diseases is largely handled with molecular genetics such as diagnosis by DNA chip. Furthermore, treatment of some diseases will be gene therapy or individually customized medicine. Yet, we must recall that there are controversial issues such as Ethico-legal social issues(ELSI). In conclusion, it is certain that this ‘genome map’ will be used for health care, and the era after the HGP is called ‘post genome’.
Single Nucleotide Polymorphism
After the human genome project and total analysis of human genome, Genome-wide association study(GWAS) has made an active advance to reveal which genes are highly related to certain diseases. However, it is still hard to find out and understand various biological pathways and phenomena. Thus, studying Single Nucleotide Polymorphism(SNP) is one of the important pieces for us. SNP is a difference of single specific nucleotide. There are approximately 3,000,000 SNPs in human genome, which appear once in 500~1,000 base pairs. When most people have the base C(cytosine) or G(guanine) at a specific position, some others could have A(adenine) or T(thymine) at the same place. SNPs might be associated with phenotype of individuals and some SNPs may cause diseases.
Human Microbiome
Microbiota is a collection or community of microbes. We humans have trillions of microbes and thought microbes as things to gotten rid of. Indeed, those are essential for human development, immunity and nutrition. Since researchers found out that the microbes in our body keep us healthy, they realized the significance of studying the genetic material of microbes, which is microbiome. Nowadays, researchers have shown that such microbial communities may highly affect some health conditions such as depression, obesity, acne, cancer, and autoimmune diseases.
Two interesting studies were published on Nature. “Maternal gut bacteria promote neurodevelopmental abnormalities in mouse offspring” and “Reversing behavioural abnormalities in mice exposed to maternal inflammation” showed that there might be some relations between the maternal gut bacteria(microbe) and offspring’s neurodevelopmental abnormalities. According to the paper, interleukin-17a(IL-17a) produced by T helper 17(TH17) cells in pregnant mice induces behavioural and corticaal abnormalities in the offsprin exposed to maternal immune activation.
The paper didn’t found out the relationship between micorbe and disease in human body, but still shows that the study of microbiome is essential. Worldwide research has been started as mapping the human microbiome, and one of thoses is Human Microbiome Project(HMP). Its goal was to identify and characterize the microorganisms in association with health or disease of human. Through this project, researchers analyzed base pairs of 178 kinds of micobes in human. They also found new 30,000 microbiome, and it shows that there are remaining tasks to reveal.
Dayoung Kim
kdayoung@unist.ac.kr
UNIST
