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The Discoveries of the Human Genome Project

April 29, 2024

Few scientific quests have sought to unravel the essence of what makes us human as the Human Genome Project. The Human Genome Project (HGP) began with the US Department of Energy launching a study to detect genetic mutations about atomic bomb survivors in Japan. Eventually, the National Institute of Health joined, along with a collection of countries across the globe, into what became a public consortium by the Human Genome Organization. HGP officially began in 1990 with a completion goal of 2005, and thus researchers set up to map the scope of homo sapien DNA, the code that determines our traits. 

Through HGP, scientists uncovered various discoveries about genetics. One such finding was that human DNA isn’t as unique as we originally thought. The genomes of people who are not closely related to each other like siblings or parents are estimated to be different by about 1 in every 1,200 to 1,500 bases. What this means is that if we consider a stretch of DNA having anywhere between 1,200 to 1,500 bases, we would expect to find one difference between the sequences, and this difference could be as small as a single letter change or single nucleotide polymorphism, or as large as differences in the number of copies of certain sections of DNA, also known as the copy number variations. Additionally,  nearly 50% of our DNA is similar to that of other organisms, with more than 40% of our proteins being similar to those of flies and worms.

Scientists also found out that genes are not evenly spread out across the 24 human chromosomes, and that some regions have many genes clustered together called rich neighborhoods, while others have few genes, known as desert areas. These desert areas consist of 20% of our genetic code, and the other 80% is made up of clustered neighborhoods. Moreover, the human genome has around 20,000 genes for protein building, which is only 2% of our total DNA. This extremely small percentage was the biggest disappointment for the scientists of the HGP, as they had hoped there would be over 100,000 genes in our genome. This discovery challenged the idea that each gene makes only one protein, and eventually led researchers to understand that the complexity of humans isn’t solely determined by the number of genes, but rather by the different ways in which genes code for proteins.

Today, we can understand that while the Human Genome Project didn’t address all the expectations and ambitions of earlier scientists, it also forever changed the landscape of the study of genetics. Through the HGP, researchers established large databases of genetic data and published to the world the human genome sequence, ensuring that the genome can be accessible at our fingertips. Moreover, in the late 1980s, computers were relatively simple, but by the time the HGP had finished, we had the internet and powerful computers to handle all this genetic data. This led to a new era of digital biology, where scientists and clinicians could analyze vast amounts of genetic information.

However, with genetic research also comes various ethical implications. One is about who should own and control genetic data – if researchers and healthcare providers should have access to it for genetic studies and patient care, there is also the issue of how ethical it is for companies to commercialize and profit from this data, especially if they sell the information to third parties. Questions around who can patent genes and genetic technologies arose and the impact this can have on genetic research and healthcare. Moreover, with sequencing the entire human genome, there also needs to be safeguards to protect the privacy and confidentiality of the participants’ genetic information from data misuse or unauthorized access. Lastly, there needs to be equitable access to the benefits of genetics research, ensuring that people of marginalized communities are not only participating in the studies, but also receive the advanced healthcare and medicine that emerges from these discoveries. 

The lessons we’ve learned from the Human Genome Project can guide us to improve our knowledge of genetics and conduct genomic research responsibly and ethically. Moreover, by understanding how our knowledge of the building blocks of humanity have evolved over time, we can develop a greater appreciation for how far science has progressed. 

 

Sources:

Collins, F. S. (1999). Medical and societal consequences of the Human Genome Project. New England Journal of Medicine, 341(1), 28–37. https://doi.org/10.1056/nejm199907013410106 

Gibbs, R. A. (2020). The Human Genome Project Changed Everything. Nature Reviews Genetics, 21(10), 575–576. https://doi.org/10.1038/s41576-020-0275-3 

Moraes, F., & Góes, A. (2016). A Decade of Human Genome Project Conclusion: Scientific Diffusion about our genome knowledge. Biochemistry and Molecular Biology Education, 44(3), 215–223. https://doi.org/10.1002/bmb.20952 

Watson, J. D. (1990). The Human Genome Project: Past, present, and future. Science, 248(4951), 44–49. https://doi.org/10.1126/science.2181665 

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.