The modern genetics revolution began with the discovery of the structure of DNA, or deoxyribonucleic acid, which is a long double-helix-shaped molecule made of complementary strings of chemical bases A, C, T and G. The particular sequence of these bases is what makes up a gene and today it is estimated that humans have between 20,000 and 25,000 genes. This set of genes, called a genome, influences an organism’s traits by coding for proteins, the building blocks of cellular life.
The Human Genome Project began as a moonshot-like attempt for scientists around the world to fully sequence the genetic code of human DNA. This project led to a technical revolution in gene sequencing technology that seems to get cheaper and more accurate year after year. This increased access to genetic sequencing has influenced many different fields of research from the identification of gene variants and their effects on health to the analysis of ancient DNA to better understand ancestral human migration patterns. Recently, there have been promising applications in medicine including increased understanding of disease risk through genetic screening and the use of gene therapy to precisely treat genetic diseases. The study of how genes are regulated, known as epigenetics, adds nuance to our understanding by showing the significant effect our environment has on the expression of genes.
Perhaps the most exciting and important recent development in genetics has come from the discovery of the genetic engineering capabilities of CRISPR-Cas9. This new technology allows programmable and specific genetic editing, e.g. allowing the replacement of faulty genes with healthy ones. CRISPR holds revolutionary promise for curing genetic disease such as sickle cell anemia or beta thalassemia and clinical trials are currently underway. The power of this new technology is immense and global cooperation to prevent its potential misuse, such as when the embryos of twin girls were edited in 2019, is increasingly vital.
The increased understanding of how genes influence biology holds enormous potential for the treatment of disease, but also brings with it some of the most important ethical questions and concerns our society has ever faced.