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What is Genome Sequencing?

August 18, 2016

In one of my recent posts, I talked about personalized medicine and how genomics will likely become standard medical practice one day, so this seemed like a great time to discuss what the term “genome sequencing” means. In my next post, I’ll go even deeper and describe something called next generation sequencing (NGS), but first, let’s cover what the genome is, why it’s important, and why we would want to sequence it.

1. What is a genome? The genome is the complete set of genetic material or genes present in an organism. It’s made of DNA, and pretty much all of your cells have a full copy of it. You inherited your genome from your parents – so you can thank them for your unique combination of traits – like eye color, hair color, height, complexion, propensity to grow weird body hair, etc.


“Gene Girls”

2. What is a gene? It’s a small region of the genome that encodes a protein. The gene acts like a blueprint and tells the cell how to synthesize that specific protein from scratch. All of your cells require proteins to survive, so these genetic blueprints are VERY important. Without proteins, your cells die (and so do you).

3. What makes up a gene? Your entire genome is made of only four chemicals, called nucleotides. They are cytosine (C), guanine (G), adenine (A), and thymine (T). These four chemicals link end to end in a specific order to “spell out” the blueprints for a protein. Just like the letters in this sentence, order is crucial for you to understand the meaning. For example… SANTA and SATAN use the same letters, but the slight differences have a big impact on meaning.


You can see why typos would be easy…

4. What is “sequencing?” This term means reading the order of the nucleotides in a gene, just like reading a book. Like a really boring book that only uses 4 letters. Sequencing can be on a small scale (single gene) or on a large scale (whole genome). For reference, the human genome has ~3 billion nucleotides.


That’s more than the number of Gangnam Style views on YouTube

Okay so now that we’ve got the basic terms, let’s talk about why sequencing the genome is so rad. First of all, it’s pretty new to us. We only finished the Human Genome Project in 2003. At the time, this was an ENORMOUS amount of work – in fact it took 13 years to complete – and it’s paved the way to new advancements in fields like molecular medicine, evolution, forensics, and so much more. And in recent years, new developments have dramatically decreased cost, making this tech more accessible to the scientific world.


In 2007, traditional “Sanger” sequencing was replaced by “Next Generation” sequencing – causing prices to plummet. More on Next Gen in my next post!

So why should you care about genome sequencing? Well, some diseases are caused by known genetic mutations, or changes in the DNA code. Sometimes they are large changes, like the deletion or rearrangement of entire genes… and sometimes they’re nothing more than a single nucleotide “typo.” We’ve been able to pinpoint the genetic mutations that cause many genetic mutations, like Huntington’s, Cystic fibrosis, Sickle cell anemia, color blindness, and some forms of cancer. But there are many, MANY more that have not yet been discovered. Easy, cheap access to genome sequencing will help researchers unlock more of these genetic mysteries.

Currently, we don’t have the technology to “fix” DNA mutations in living humans, but understanding the root of genetic disorders will allow researchers to develop these types of cures. It may seem like science fiction, but scientists have actually been working on gene therapy methods for years. With access to cheap, reliable genome sequencing these efforts will be accelerated – and medical science will certainly benefit! Now we just need servers that can handle the tsunami of data we’re going to generate…



From → Biology

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