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6.9: The Human Genome

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    Vitruvian Man

    The drawing in Figure \(\PageIndex{2}\), named Vitruvian Man, was created by Leonardo da Vinci in 1490. It was meant to show normal human body proportions. Vitruvian Man is used today to represent a different approach to the human body. It symbolizes a scientific research project that began in 1990, exactly 500 years after da Vinci created the drawing. That project, named the Human Genome Project, is the largest collaborative biological research project ever undertaken.

    Vitruvian man
    Figure \(\PageIndex{1}\): Vitruvian man

    What Is the Human Genome?

    The human genome refers to all the DNA of the human species. Human DNA consists of 3.3 billion base pairs and is divided into more than 20,000 genes onto 23 pairs of chromosomes. The human genome also includes noncoding sequences (e.g. intergenic region) of DNA, as shown in Figure \(\PageIndex{2}\).

    Discovering the Human Genome

    Chromosomes along with 2 genes and intergenic region illustration
    Figure \(\PageIndex{2}\): Human Genome, Chromosomes, and Genes. Each chromosome of the human genome contains many genes as well as noncoding intergenic (between genes) regions. Each pair of chromosomes is shown here in a different color.

    Scientists now know the sequence of all the DNA base pairs in the entire human genome. This knowledge was attained by the Human Genome Project (HGP), a $3 billion, international scientific research project that was formally launched in 1990. The project was completed in 2003, two years ahead of its 15-year projected deadline.

    Determining the sequence of the billions of base pairs that make up human DNA was the main goal of the HGP. Another goal was mapping the location and determining the function of all the genes in the human genome. There are only about 20,500 genes in human beings.

    A Collaborative Effort

    Funding for the HGP came from the U.S. Department of Energy and the National Institutes of Health as well as from foreign institutions. The actual research was undertaken by scientists in 20 universities in the U.S., United Kingdom, Australia, France, Germany, Japan, and China. A private U.S. company named Celera also contributed to the effort. Although Celera had hoped to patent some of the genes it discovered, this was later denied.

    Reference Genome of the Human Genome Project

    In 2003, the HGP published the results of its sequencing of DNA as a human reference genome. Figure \(\PageIndex{4}\) illustrates the process of DNA sequencing. The details of this image are out of the scope of this concept and book. The sequence of the human DNA is stored in databases available to anyone on the Internet. The U.S. National Center for Biotechnology Information (NCBI), part of the NIH, as well as comparable organizations in Europe and Japan, maintain the genomic sequences in a database known as Genbank. Protein sequences are also maintained in this database. The sequences in these databases are the combined sequences of anonymous donors, and as such do not yet address the individual differences that make us unique. However, the known sequence does lay the foundation to identify the unique differences among all of us. Most of the currently identified variations among individuals will be single nucleotide polymorphisms or SNPs. An SNP (pronounced "snip") is a DNA sequence variation occurring at a single nucleotide in the genome. For example, two sequenced DNA fragments from different individuals, GGATCTA to GGATTTA, contain a difference in a single nucleotide. If this, base change occurs in a gene, the base change then results in two alleles: the C allele and the T allele. Remember an allele is an alternative form of a gene. Almost all common SNPs have only two alleles. The effect of these SNPs on protein structure and function and any effect on the resulting phenotype are an extensive field of study.

    Benefits of the Human Genome Project

    The sequencing of the human genome holds benefits for many fields, including molecular medicine and human evolution.

    • Knowing the human DNA sequence can help us understand many human diseases. For example, it is helping researchers identify mutations linked to different forms of cancer. It is also yielding insights into the genetic basis of cystic fibrosis, liver diseases, blood-clotting disorders, and Alzheimer's disease, among others.
    • The human DNA sequence can also help researchers tailor medications to individual genotypes. This is called personalized medicine, and it has led to an entirely new field called pharmacogenomics. Pharmacogenomics, also called pharmacogenetics, is the study of how our genes affect the way we respond to drugs. You can read more about pharmacogenomics in the Feature below.
    • The analysis of similarities between DNA sequences from different organisms is opening new avenues in the study of evolution. For example, analyses are expected to shed light on many questions about the similarities and differences between humans and our closest relatives the nonhuman primates.
    Human Genome Project Timeline
    Figure \(\PageIndex{3}\): Timeline of the human genome project from 1990 to 2003. The details of this timeline are more than we need here. You can see all the details at the NIH site.

    Ethical, Legal, and Social Issues of the Human Genome Project

    From its launch in 1990, the HGP proactively established and funded a separate committee to oversee potential ethical, legal, and social issues associated with the project. A major concern was the possible use of the knowledge generated by the project to discriminate against people. One issue was the fear that employers and health insurance companies would refuse to hire or insure people based on their genetic makeup, for instance, if they had genes that increased their risk of getting certain diseases. In response, in 1996, the U.S. passed the Health Insurance Portability and Accountability Act (HIPAA). It protects against unauthorized, nonconsensual release of individually identifiable health information to any entity not actively engaged in providing healthcare to a patient. This was followed in 2008 by the Genetic Information Nondiscrimination Act (GINA), which specifically prohibits genetic discrimination by health insurance companies and workplaces.


    1. Describe the human genome.
    2. What is the Human Genome Project?
    3. Identify two main goals of the Human Genome Project.
    4. What is the reference genome of the Human Genome Project? What is it based on?
    5. Explain how knowing the sequence of DNA bases in the human genome is beneficial for molecular medicine.
    6. What was one surprising finding of the Human Genome Project?
    7. Why do you think scientists didn’t just sequence the DNA from a single person for the Human Genome Project? Along those lines, why do you think it is important to include samples from different ethnic groups and genders in genome sequencing efforts?
    8. True or False. The sequenced human genome does not include noncoding regions — it only includes actual genes.
    9. True or False. Knowing the sequence of the human genome can give insight into human evolution.
    10. What is pharmacogenomics?
      1. If a patient were to have pharmacogenomics done to optimize their medication, what do you think the first step would be?
      2. List one advantage and one disadvantage of pharmacogenomics.
    11. There are approximately 20,000 human
      1. base pairs
      2. nucleotides
      3. alleles
      4. genes
    12. Explain how the sequencing of the human genome relates to ethical concerns about genetic discrimination.

    Explore More

    For years, scientists have had the challenge of sequencing the human genome. Learn more about the human genome project here:


    1. Vitruvian man public domain via Wikimedia Commons
    2. Human genome to genes by LoStrangolatore, CC BY 3.0 via Wikimedia Commons
    3. Human genome project by National Human Genome Research Institute (NHGRI), licensed CC BY 2.0 via Wikimedia Commons
    4. Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0

    This page titled 6.9: The Human Genome is shared under a CK-12 license and was authored, remixed, and/or curated by Suzanne Wakim & Mandeep Grewal via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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