It’s All In The 👖
A beginner’s guide to the past, present, and future of genomics
In a world full of divisive opinions and conflict, it can be easy to forget how much we all really have in common — starting with the very building blocks of life. 🧱
Genomics is a field that has long captivated humanity as we yearn to discover what these mysterious “genes” hold that allow us to be so similar yet so different at the same time.
A Crash Course In High School Biology
Every living thing is made up of cells, scientifically termed eukaryotic cells. The human body itself is composed of trillions of these cells, at the crux of which, a chemical compound known as deoxyribonucleic acid (or DNA) is found in the nucleus. DNA carries the genetic code for proteins and stores and transmits hereditary information. It is unique for everyone, except for identical twins. 👪
An important part of DNA is nitrogenous bases (rings of carbons and nitrogens), which are defined as either purines or pyrimidines based on their structure. Pyrimidines are further categorized into Thymine and Cytosine, while purines branch into Adenine and Guanine. Purines are complimentary to pyrimidines, allowing the nitrogenous bases to form hydrogen bonds with one another. Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C).
And, so, we’ve reached the fun part — genes, genes, and more genes! 🧬
A gene, by definition, is a unit of inherited material. DNA is housed in structures called chromosomes, each of which consists of small segments (yup, you guessed it: genes!) located at specific positions.
The last concept to note is that our bodies have both somatic (body) and gamete (sex cells). Somatic cells are the vast majority of cells, and gamete cells are sperm / egg cells that will aid in reproduction. Somatic cells undergo a process called mitosis for cell division, and gamete cells undergo meiosis, with the latter having some key differences to ensure genetic variation (e.g. crossing over, random assortment, etc.)
Genomics: What Is It & Why Should You Care?
Genomics is the study of an organism’s DNA. A genome refers to all the DNA contained within cells in the body, which has been coiled to fit into tightly-packed chromosomes. As we learned previously, DNA is the code of life, fundamentally made up of 4 nitrogenous bases, but the order of this code changes from person to person. Each cell has 23 pairs of chromosomes, within each pair, one of which is from the mother, and the other from the father. Understanding genomics can help to treat disease 🩺, and allow us to understand more about ourselves on the micro-scale, such as genetic susceptibility to certain traits and / or behaviours 💭.
Variants in genes dictate differences between individuals. Those affecting a single position are single nucleotide variants (SNVs). SNVs along with larger DNA changes, such as deletions, duplications, rearrangements, etc. — pretty much exactly what they sound like in relation to gene position — cause genetic diversity.
Genomics is a rapidly evolving field, which is giving rise to technologies and disciplines, such as gene-editing, precision medicine, and synthetic biology. As NatGeo put it, this could very well be “a revolution in health care.”
The Past: Genetic Theories
It is nearly impossible to discuss genetics without mentioning Gregor Mendel; the father of modern genetic theories. Mendel was interested in how traits passed from generation to generation, with his research primarily focused on the sexual reproduction of pea plants through self-fertilization. 🌱
Mendel’s experiments led him to realize that certain traits don’t disappear, but are rather just unexpressed — contrary to popular belief at the time. He also concluded that traits are encoded by genes on chromosomes, which always come in pairs. Dominant alleles can overpower the expression of recessive genes. These findings, coupled with others, led to the formation of Mendel’s laws…
- Law of Segregation: alleles separate from each other in the formation of gametes, and dominant traits will always appear when the individual has the dominant allele, whereas recessive traits only appear when the individual has 2 recessive alleles.
- Law of Independent Assortment: genes for different traits arrange independently of each other when gametes are formed.
Since Mendel’s time, other genetic theories have also emerged. Incomplete dominance describes a condition wherein neither of the 2 alleles for the same gene can completely conceal presence of the other allele, leading to an “in-between” appearance. On the flip side, codominance occurs when both alleles are fully expressed, leading to a mixed appearance. Scientists have also become aware of multiple allelism, which is when multiple alleles (2+) are present for a single gene, such as blood types. Additionally, polygenic traits are influenced by 2 or more genes — up to 60 genes can influence skin colour!
The Present: Genome Sequencing
Despite advances in our understanding of the human genome, scientists continue to strive towards more efficient and effective mechanisms to bring us ever closer to unravelling the genetic mysteries that continue to elude humanity. 🕵️ As such, genomic sequencing remains a powerful biological tool.
Fundamentally, genomic sequencing is the process of taking a DNA sample and inserting it into a sequencing instrument. This instrument uses high frequency sound waves to break the DNA down into smaller pieces, roughly 600 bases long. After adding special tags to the ends of DNA strands — allowing them to attach to glass slides — the sequencer will then copy the DNA many times to create identical DNA fragments. This is done because of the miniscule nature of the original genome, so by having multiple identical copies of the sequence, it becomes easier to work with. The sequencer then reads the DNA, one base at a time, and tags each base with a different colour. The machine is equipped with special sensors that detect the colours, thus revealing the sequence of each individual DNA fragment. Lastly, computers are used to piece the fragments back together.
The challenge now facing scientists is no longer how to sequence the genome, but rather, how to effectively use the information it provides to make important decisions.
The Future: Genomics of Tomorrow
Genetic Engineering
As genomics continues to evolve, many have turned their attention and resources to the emerging field of genetic engineering — essentially, altering the genetic makeup of an organism.
The most recognizable gene-editing technology is likely CRISPR-Cas9. Based on a natural bacterial defense mechanism to protect against viral infections, CRISPR-Cas9 uses the protein Cas9 to cut, edit or repair DNA. Genome editing via CRISPR-Cas9 has already been used to reduce hearing loss in mice carrying a genetic mutation for deafness! 🐁
Although genetic engineering’s use in living organisms (especially humans) is still a matter of hot debate, the technology has already become mainstream in other facets of everyday life. For example, the use of GMOs in produce has become quite commonplace, such as Arctic apples which don’t brown when exposed to the air. 🍎
Cool Companies Doing Cool Things!
Today, many companies have turned to genomics as their industry of choice. Some groundbreakers in the world of genomic enterprises include 23andMe, Foundation Medicine, and SHERLOCK.
First up, 23andMe is a genome sequencing company which gives customers diagnostics revealing information about ancestry, traits, health, etc. The business aims to promote the accessibility of genomic information for all.
Next, Foundation Medicine is a venture that connects physicians and patients to cancer treatment approaches by making precision medicine (treatments based on genetics) more widely available. The process consists of genomic testing to understand the genomic makeup of tumour, following which the tumour’s genomic profile is matched to cancer treatments, such as immunotherapies or clinical trials. Lastly, the information is compared to Foundation Medicine’s own cancer genomic databases, and partnerships are forged with drug developers.
Lastly, SHERLOCK is a revolutionary miniature paper test, similar to a pregnancy test, which takes just minutes to predict diseases from DNA! The test has previously been used to detect Zika and Dengue virus simultaneously. SHERLOCK uses the protein complex Cas-13, which can be programmed to bind to a specific piece of RNA. In certain circumstances, once Cas-13 locates and cuts the target, the enzyme will go into overdrive by cutting other nearby RNA. Subsequently, additional synthetic strands of DNA are used to create a signal after being cut, and will release a signal indicating the presence / absence of the target.
Key Takeaways
In two words, genomics is SUPER COOL! Rapidly evolving, with advancements being made all the time, it’s hard not to wonder what secrets our DNA really holds. 🤔
To summarize…
- Every cell in the human body has DNA, which consists of genes — units of inherited material. Nitrogenous base pairings are A-T and G-C. Our bodies have both somatic (body) and gamete (sex cells). Somatic cells divide through mitosis, and gamete cells divide through meiosis.
- Genomics is the study of an organism’s DNA. Understanding one’s genome can help to treat disease, and has created new technologies like gene-editing, precision medicine, and synthetic biology.
- The Past: Genomic theories include Mendel’s laws, incomplete vs. codominance, multiple allelism, and the polygenic nature of some traits, all of which are crucial to our understanding of genomics today.
- The Present: Tools such as genome sequencing allow us to gain a better understanding of the human genome, on an individual level.
- The Future: Genetic engineering is a fascinating emerging field spearheaded by the use of CRISPR-Cas9. Companies experimenting with products in the genomics realm include 23andMe, Foundation Medicine, and SHERLOCK.
