Genetics and genomics are very similar disciplines, they both focus on the DNA of an organism with the major difference being scope. Genetics refers to the genes within a genome whereas genomics refers to the genome as a whole. Studying both genetics and genomics is important as seen in the application of the technologies to medicine.
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The root cause of disease varies, some diseases are caused by the inheritance of specific defective genes but most diseases come from the complex interplay between environmental factors and the body’s response. Therefore, genetics plays a role in understanding diseases that are caused by specific defective genes, whereas a wider gnomonic approach is required to tackle the more complex problem of how the genome and environment interact. This illustrates how both technologies have their place in the research toolbox.
Genetics is the study of genes, how mutations affect the functioning of a gene, and how this may spread through a population. Before genes could be studied through DNA sequencing, they could be traced through the effect on the phenotype. This method of studying genetics is called classical genetics whereas other methods include molecular genetics which uses a combination of cloning and DNA sequencing to track genes and study their products.
Classical genetics was pioneered by Gregor Mendel who studied pea plants. He tracked the outward appearance of the pea plants while carefully controlling any cross-breeding. Through these careful observations, he noticed that some phenotypes skipped a generation and came up with the theory of each plant having two copies of a gene, one from each parent, furthermore these genes could be dominant or recessive.
The phenotype of a dominant gene will show over that of a recessive gene but this recessive gene may be passed onto the next generation, where, if neither gene is dominant then the recessive gene’s phenotype will be shown.
Through this method, the spread of certain phenotype-linked genes through a population can be studied. This changed with the advent of DNA sequencing allowing classical genetics to be applied to genes without an associated phenotype, while the advent of molecular genetics allowed for the study of gene products.
Molecular genetics goes beyond studying the sequence of naturally occurring genes. In molecular genetics, DNA fragments carrying the gene of interest can be placed into a bacterial plasmid. These modified plasmids are grown and expressed in bacteria, thereby allowing their protein products to be studied. Through this method, the variation seen in genes can be studied to see how they affect the proteins that are produced.
Furthermore, these fragments of DNA can be intentionally mutated thus permitting the study of specifically mutated genes advancing the understanding of the role the gene plays. However, this does not consider the role of regulatory genomic elements, that requires the entire genome to be studied.
As the field of genetics developed with advancing technology, it provided the opportunity to sequence the genome as a whole. Genomics is the study of the genome as a whole.
The ability to sequence an entire genome is a relatively recent advancement. It took a decade and cost billions of dollars to sequence the first human genome but by 2016 a genome could be sequenced for around US$1,000. This creates a whole new dimension to the study of DNA and gene expression because contained within DNA are regulatory elements that affect the expression of genes.
Genomic Possibilities and Challenges
Being able to sequence an entire genome opens up many different possibilities including the ability to create clinical trials by carefully selecting patients that are more likely to have an event or trace human evolution through genetic make-up. However, one challenge in the study of genomics, particularly human genomics, is selection bias. The majority of sequenced genomes come from people of European descent skewing any data and conclusions.
As of 2019, around 80% of sequenced genomes come from individuals of European descent and that figure falls to around 10% for those of East Asian heritage and only around 2% of African descent. This could have serious effects as many variations come from the regulatory regions controlling the expression of genes not just from the genes themselves. Genomes from those of African descent are among the most diverse and without sequencing, this wealth of information cannot be used to improve medical care and understand their unique risk factors.
Genetics and genomics are fields of research that have undergone great advancements in recent years which has opened many possibilities. Genetics has evolved from studying the action of genes through their phenotypic appearance to the molecular expression of genes and their sequencing. This has allowed for the study of genes throughout a population, their heritability, and variation.
Whereas genomics has allowed for the study of the entire genome of an organism. This has allowed for research that is beyond just the genes and encompasses the regulatory regions that may be responsible for the further variation seen within the population as a whole. Demonstrating not only the similarities but also the differences between these two techniques.
- Epstein, C. J. (2006). Medical genetics in the genomic medicine of the 21st century. American Journal of Human Genetics, 79(3), 434–438. https://doi.org/10.1086/507610
- Health, W. (1997). Report of the advisory committee on health research. Revista Panamericana de Salud Publica/Pan American Journal of Public Health, 2(6), 428–434. https://doi.org/10.1590/S1020-49891997001200014
- McGuire, A. L., Gabriel, S., Tishkoff, S. A., Wonkam, A., Chakravarti, A., Furlong, E. E. M., Treutlein, B., Meissner, A., Chang, H. Y., López-Bigas, N., Segal, E., & Kim, J. S. (2020). The road ahead in genetics and genomics. Nature Reviews Genetics, 21(10), 581–596. https://doi.org/10.1038/s41576-020-0272-6