Video Transcript
In this video, we’ll learn about the Human Genome Project, along with its applications, such as in medicine, and how its potential impacts have stimulated far-ranging ethical discussions. The Human Genome Project was completed in 2003 after 13 years of effort by many scientists from several different countries. The primary goal of the Human Genome Project was to sequence a human genome, so let’s start by finding out what a genome is. What molecule is common to these words? Gene, genetics, and genome.
The most obvious answer to that question is DNA. DNA contains a chemical code that we use to store information about ourselves. The genome is all of an individual’s genetic information, and that’s stored in their molecules of DNA. And surprisingly, we have all of our genetic information in almost every cell of our bodies. You’ll find most all of your DNA in the nucleus of your cells, where it coils up into structures called chromosomes.
Our chromosomes come in highly similar pairs because we get one of each pair from one of each of our parents. So we get 23 chromosomes from our fathers and 23 highly similar but not completely identical chromosomes from our mothers. So scientists from the Human Genome Project sequence sections of DNA from several anonymous volunteers and then piece these sections together into one DNA sequence for a human. A genome contains a lot of information though. So since each chromosome of a pair is more than 99 percent identical to the other, complete information from only one chromosome of a pair was recorded in what is referred to as our reference genome. Only variations from the most common base sequences were recorded as more than one chromosome of a pair was sequenced.
This still left the scientists with over three billion pieces of information to analyze and record. So the Human Genome Project set about to identify the genetic information contained in one set of human DNA molecules. And next we’re gonna learn about what exactly that information is that they uncovered. We know that our genetic information is stored in a chemical code in DNA molecules that coil up into structures called chromosomes. And you have a complete set of chromosomes in almost all your cells. Our paired chromosomes that come from our mothers and our fathers have the same genes in the same location. A gene is a section of DNA that generally codes for protein, and they lead to the expression of our characteristics. Common examples of human characteristics include things like the color of your eyes, the color of your hair, and if your hair is curly or straight; that’s hair texture.
We can see that the dad and the mom of the owner of these chromosomes here do have colored eyes and colored hair, and their hair has texture, but they’re not exactly the same. The dad’s eye color gene codes for blue eyes, but the mom’s eye color gene codes for green eyes. The mom’s DNA produces blonde hair, while the dad’s DNA produces black. And differences in their hair texture gene gives them different textured hair. The term used to describe different versions of the same gene is allele. The dad of the chromosomes’ owners has a blue eye allele, an allele for black hair, and an allele for straight hair, while the mom has alleles for green eyes, blonde hair, and curly hair.
One more thing about chromosomes though, if you’ve seen them in this shape before where they look more like a letter X, then they’re replicated chromosomes, and they contain two identical DNA molecules. But the human genome scientists didn’t wanna double their work. They only wanted to sequence one DNA molecule from each of the chromosomes. So how can you tell a blue eye allele from a green eye allele when you’re looking at the DNA? That’s when you have to start to look at the chemical code of DNA, which is written in these four letters A, T, G, and C. These letters represent the four bases of DNA. A stands for adenine, and it always bonds across the DNA molecule to the base T or thymine. G stands for guanine, and it always bonds across the DNA molecule to the base C or cytosine.
If you could untwist a DNA molecule, like the one here, it would look sort of like a ladder. And the steps of the ladder would be these AT and CG combinations, and we call those base pairs. This is very convenient because if you find the order or sequence of bases on one strand of DNA, you’ll automatically know the sequence or order of bases on the other strand. We already noted that the genetic information in human chromosomes is highly similar between individuals. But between alleles of the same gene, such as our blue eye and green eye alleles here, there must be some differences in the order of bases. These differences in the DNA sequences are called variants, and they explain why although we have common characteristics we can still have differing traits within them.
So the goal of the Human Genome Project was to sequence the order of bases in each human chromosome, and they used samples from several volunteers. And the result was a long, long list of these genetic letters A, T, Cs, and Gs, more than three billion of them. So the goal of the Human Genome Project was just the beginning. It left a map for future scientists to explore for the location of genes and their different alleles, with the hope that this knowledge would benefit our species. By the time they had finished, they had enough As, Ts, Cs, and Gs to fill 175 very large books. But luckily, we don’t have to write whole genomes in books. Computer technology was advancing at the same time and helped the Human Genome Project immensely.
When the Human Genome Project started, scientists were able to sequence a few hundred DNA bases per day. But technology advanced throughout the project, and now we can sequence thousands of DNA bases per second. The integration of computing power into sequencing technology is responsible for some of these advances. But another big part was just the collaboration or the working together of many scientists who learn from each other along the way. The term genomics was coined during the Human Genome Project. It’s the study of genome structure, function, and evolution. And both the results of the Human Genome Project and the growing science of genomics are used in different applications, including many advancements in medical treatments, uncovering ancient patterns of human migration across the globe, and providing direct evidence of evolutionary processes.
Next, let’s take a look at how the analysis of genetic information can lead to such advancements. The Human Genome Project identified the order of bases in human DNA molecules, which were isolated from our chromosomes. That’s called DNA sequencing. Many genomes have been sequenced since the Human Genome Project, and the information from them has been used to maintain a reference genome for humans that contains the most common bases along our DNA molecules. Now, when genomes are sequenced, they can be compared to this reference genome.
Here’s a very simplified example. Let’s say we have 1000 sections of DNA from people with brown eyes and 1000 from people with blue eyes. And we compare each of these sections to the same section on the human reference genome. The DNA sequence from people with brown eyes exactly matches the reference genome, as does the order of bases for the people with blue eyes, except for one variant. Here we have an AT base pair, where both the other genomes have a GC base pair.
Does that mean that this variant causes blue eyes? The answer is maybe it does, and maybe it doesn’t. Variations that are found to be associated with certain traits need to have more conclusive research to find if they actually cause them. This sort of analysis is a huge help to finding out what parts of the genome should be researched further. This approach can be used in medicine to find associations between certain variants and certain genetic disorders or even to find unique variants in individuals that are suffering from an unknown disease. This is called personalized medicine, and it helps medical professionals predict, diagnose, and treat individuals based on their own information. The prediction of disease doesn’t just affect individuals. It can also affect their relatives because they’ll find out more about themselves as well, including any offspring the tested individual might have.
The diagnosis of genetic disease in individuals can also help in the prediction of that disease for their relatives. So the use of genomics and personalized medicine has helped many individuals with genetic disorders, such as cystic fibrosis, or cancer, such as breast cancer caused by mutations in the BRCA genes, and even other diseases that are only partially affected by your genetics, such as type 2 diabetes.
Genomics has also been used to find patterns in how our ancestors migrated around the world. Ancestral populations that stay together for many, many generations can accumulate many common variants between them. Over time, smaller groups of humans left the larger population and went to different areas. But these small groups could only carry some of these ancestral variants with them. And as these populations grew generation by generation, they started to get new mutations, which are accidental changes in DNA. And those can lead to unique variants.
Analysis of the gain and loss of variants in humans alive today has allowed scientists to piece together patterns about how our ancestors migrated from Africa to other continents across the globe. So genomics helps to reveal our connections to our ancestors, but not just our human ancestors. We now have reference genomes for many species on the planet. One of the basic assumptions of this type of analysis is that greater genetic similarity indicates more recently shared ancestry. We’ll use an example that still involves humans. Neanderthal DNA has been found to be about 99 percent the same as our own. And scientists estimate that our most recent common ancestor that we shared with Neanderthals existed about 800000 years ago.
We share less of our DNA with chimps than we do with Neanderthals, so we would infer that our most recent common ancestor that we shared with chimps existed even further back in time. And using the same logic, since we only share about 50 percent of our DNA in common with plants, we’d infer that our most recent common ancestor that we shared with them was even much further back in history. Despite all we’ve learned from the Human Genome Project and genomics, there are some very real concerns about where this all might lead.
One concern about revealing your genetic information is that it could be used against you. One example of this involves health insurance companies. If a health insurance company finds that you have variants that are associated with disease, they may be inclined to charge you higher premiums or not ensure you at all. Employers can also use your genetic information to discriminate against you if you have certain variants that seem like they’re too much of a risk for their company. Some countries have enacted laws to protect people from this kind of discrimination. But other types of insurance, such as life insurance or disability, might not be included in those laws.
A deeper fear is that the science of genomics could be used to support practices in eugenics. The goal of eugenics is to improve our species. And while that might seem noble, people who have tried doing this in the past have used blatantly unethical means. One example of the practice of eugenics occurred in the United States in the mid-1900s. Some people were judged to be inferior for one reason or another and were forcibly sterilized so they could no longer have children. Genomics is getting to the point where we can start directing our own evolution, and that’s pretty scary. Is that something we should really engage in? The future will probably be a balancing act between individual and societal concerns and the collective health gains that we might experience through genomics.
Here’s some key points from the video. The Human Genome Project identified the sequence of DNA bases in a human genome, and a genome is all of an organism’s genetic information. This effort took 13 years, and it was finally completed in the year 2003. This massive effort required the collaboration or the working together of many scientists from several countries, and it also led to the science of genomics. Computers were an essential tool in the Human Genome Project because there was so much data to process and share. The Human Genome Project and genomics have led to advances in medicine, including predicting, diagnosing, and treating genetic disorders, certain types of cancers, and even other disorders that only have genetic components.
Studying the variation in DNA between humans has helped us understand how our ancestors spread across the globe. And we can compare the DNA of different species to better understand their evolutionary relationships. But this knowledge has also led to concerns. One is about our privacy of genetic information. If others find out about our genetics, they might be able to use it to discriminate against us. An even deeper fear is that genomics could be used in the practice of eugenics.
