Ten years after the first rough draft of the human genome was unveiled in 2000, opinions appear varied on the success of the Human Genome Project -- an ambitious multibillion-dollar project to map the entire human genetic code and to learn more about the genetic underpinnings of disease. A series of New York Times articles in June 2010 criticized the project for not leading to many new cures for diseases [source: Wade and Pollack]. Another repeated point has been that the project has been more fruitful for scientists than medical researchers.
But many scientists took issue with the New York Times' assessment. One Harvard Medical School professor wrote that the project should be appreciated for the opportunities it's provided to study human health on a molecular level and for the insights it's provided to a range of medical and biological sciences -- not just drug research. He went on say that the project "may be the most effective $3 billion ever spent by this country" [source: Farzan].
Whatever the individual views on the success of the Human Genome Project may be, there's no doubting that science's understanding of genes, and what they tell us about our bodies, has progressed immensely in recent decades. We now know far more than we did even a decade ago about how our genes are ordered and what many of them do. In this article, we'll take a look at 10 things our genes can tell us -- from blood type to disease; from where our ancestors came from to how long we might live.
10. Blood Type
Your blood is one of the many fundamental bodily functions defined by what lies in your genetic code. Your blood may have one of four combinations of agglutinogen -- proteins that bind to red blood cells and that are known by their letter abbreviations: A, B, AB or O (meaning the absence of any agglutinogen). Agglutinogen type is dictated by what genes are inherited from the parents. If you receive the A and B alleles (variations of a gene) from, respectively, your father and mother, then you will have a blood type of AB. Type O blood means that the person in question has the O allele, which produces a nonworking protein [source: Genetic Science Learning Center]. Because the O allele doesn't affect blood type, any combination of an A or B allele with an O allele produces either type A or type B blood.
When we speak of positive or negative blood type, we're referring to the presence, or absence, of a protein called Rh. The gene that determines one's Rh factor has two possible alleles. Someone who is Rh-, or has a "negative" blood type, must have an Rh-/Rh- genotype. (Genotype is the particular combination of alleles one has for a given trait.) But a person needs to only have one Rh+ allele in order to have a positive blood type [source: The Biology Project].
These are the main genetic factors dictating blood type, but scientists have discovered dozens of genes that affect blood in one way or another -- from cholesterol to triglyceride levels to one's susceptibility to blood-related diseases.
9. Physical Characteristics
All of our physical features -- save such things as scars or plastic surgery -- are dictated by our genes, and these genetic traits are passed on to us from our parents in the form of 23 pairs of chromosomes. Genes determine whether your ear lobes are attached or detached and how big they are. Genes determine your height, the color of your hair and eyes, the shape of your nose and whether you have dimples.
Tongue rolling -- curling your tongue into a taco-like formation -- is generally believed to be a genetically determined dominant trait. But some studies found that in 30 percent of identical twins, only one of the two siblings possessed this ability -- a discrepancy that has called into question whether the trait is genetically defined [source: Genetic Science Learning Center].
Physical traits are often described as either dominant or recessive -- that is, one allele is dominant over another, meaning that if both are present in a person's genome, the dominant allele will manifest itself in the form of a physical characteristic. However, some genes are co-dominant, meaning that they both will affect a physical trait, and as researchers' understanding of the human genome has progressed, many features once believed to be determined by a single gene have been shown to be the product of two or more genes.
8. Paternity, Maternity and Relatives
Our family histories are written in our genes. Each person has 46 chromosomes -- two sets of 23 chromosomes derived from the genetic material passed on by his or her parents. It's random which chromosomes a child inherits from each parent, yet DNA analysis allows scientists to trace a child's family lineage with extraordinary accuracy -- up to 99.9 percent if done properly [source: Great Lakes Genetics]. Paternity testing usually is done with a blood sample, cheek swab or other tissue sample; maternity testing follows the same basic method.
A lab paternity test may cost from a few hundred dollars to $2,000 [source: American Pregnancy Association]. There are relatively cheap paternity tests available from e-commerce sites or over-the-counter at pharmacies, though these require additional fees in order to obtain the lab results and many of them have not been evaluated by the U.S. Food and Drug Administration [source: Pollack]. The accuracy of such tests may also be an issue, as home practitioners may not properly collect swabs or prevent them from being contaminated [source: Aleccia].
Kinship tests can also be performed to see if people are siblings or otherwise related. In these cases, testing services examine DNA samples to find common genetic markers, allowing them to chart lineages through shared DNA.
7. Genetic Disorders
Genetic disorders, or hereditary diseases, occur because of a harmful mutation in a person's DNA. Examples of genetic disorders include Down syndrome, cystic fibrosis and even some types of cancer. The origin of some genetic disorders remains unknown, but the unraveling of the human genome has allowed scientists to chart the origin of many others.
Genetic disorders can generally be divided into four categories: single-gene disorders, chromosome abnormalities, multifactorial disorders and mitochondrial disorders [source: Genetic Science Learning Center and Human Genome Project Information]. Single-gene disorders are what they sound like: disorders caused by a crucial mutation within a single gene. Chromosome abnormalities are problems with parts of chromosomes, although in some cases, a whole chromosome may be missing or duplicated. (Down syndrome is one well-known chromosome abnormality.)
Multifactorial disorders are caused by a combination of several genetic abnormalities. Environmental causes (such as exposure to toxic chemicals) may also play a role. Several common types of cancer, including breast and colon cancer, fall under the category of multifactorial disorders. Mitochondrial disorders, on the other hand, are rather rare but can be serious, sometimes involving several symptoms affecting multiple organs or neurological function.
6. Ancestral Lineage
Genetic genealogy, or the study of ancestral DNA, looks at how a population's DNA changes over periods of hundreds or even thousands of years. By charting changes and common markers in the DNA of various ethnic, national, religious or other groups, scientists can often learn about a population's lineage and to which groups -- past and present -- the population might be related. If we go back far enough -- about 60,000 years -- we find that all humans trace their ancestry back to a population from the African continent [source: The Genographic Project].
There are several different ways in which scientists pursue genetic genealogy. Maternal lineage can be tracked through mitochondrial DNA (mtDNA) -- the DNA of the mitochondria, which provides energy to cells. Mitochondrial DNA is passed down exclusively from the mother to her child, making it easier to chart its progression over generations. While mtDNA is passed down to both boys and girls, Y-DNA is passed down exclusively from fathers to sons (as only males have Y chromosomes), making Y-DNA a way to track paternal lineages over generations.
Many private companies now offer personalized genetic testing services, and a common product among these services is an examination of one's family history by way of genetic genealogy. Such services have proven useful for people who may not know where their ancestors came from, such as modern-day descendents of African slaves, who can often learn with a relatively high degree of accuracy to which ethnic group their ancestors belonged.
5. Relationships with Other Species
Decoding the human genome has provided the raw data for numerous studies examining how our species is related to other great apes, particularly chimpanzees, and many other animals. In this field, known as comparative genomics, scientists can compare DNA between species in order to learn more about how genetic mutations cause disease in humans.
A large number of mammals -- anything from mice to apes, as well as humans -- are believed to have genomes made up of about 3 billion base pairs [source: Stubbs]. However, just because humans and dogs each have 25,000-odd genes doesn't mean that we're closely related. We have as many as 98 percent of our genes in common with great apes and 85 percent with mice, but that still leaves room for thousands of different genes that prove crucially consequential [source: Stubbs]. When considering that many human characteristics and bodily functions require the complex interaction of many protein-encoding genes, even a difference of 2 percent (as is the case with humans and chimps) can be considered immense.
Yet these similarities, such as they are, can tell us a lot about the human genetic code and how it's evolved. For example, because they reproduce easily and quickly and have the same approximate number of genes as humans, scientists often tinker with mice genomes, turning individual genes off and on and then studying the effects. The results may not please animal rights activists, but such studies often produce useful data regarding the roles of certain genes that we share with these little creatures.
4. Late-in-life Diseases
Genetic testing has created a raft of possibilities for learning more about our genes and what they may tell us about our health. People are increasingly using genetics for its predictive powers -- to find out what genetic mutations they might have, and what these mutations may augur for their future health.
The BRCA1 and BRCA2 (often pronounced BRACK) genes normally help the body to prevent uncontrolled cell division; in other words, they stop the body from developing tumors. However, if these genes possess certain mutations, a person's likelihood -- male or female -- of developing breast cancer greatly increases [source: National Cancer Institute].
Some genetic mutations are not problematic and certain mutations on the BRCA1 gene may be more harmful than some on the BRCA2 gene (and vice versa). Even so, 60 percent of women with a harmful BRCA gene mutation will develop breast cancer -- an increase of almost 40 percent over those with normal BRCA genes [source: NCI].
There are numerous other genes found to be associated with various types of cancer, such as p53, which is also considered a "tumor suppressor" gene. Many of these genes interact in ways still unclear to scientists [source: National Institute of Health]. However, identifying some of these genes through genetic testing often allows for preventive medicine. People who have tested positive for harmful gene mutations may choose to increase their screening regimen (for example, they might schedule more frequent mammograms) or have prophylactic surgery. With the prophylactic procedure, tissue from the area in question is removed in order to head off tumors before they have a chance to form.
In the world of 21st century medical care, "personalized medicine" is a buzz phrase, and as we seek out specialized treatments for serious diseases, pharmacogenomics will help us get there. Pharmacogenomics examines how an individual's particular genome responds to drugs and whether drugs can be tailored to a person's unique genetic profile.
Many of the promised breakthroughs of pharmacogenomics remain years away. But the potential is enormous. If drugs could be customized to respond to a person's genetic makeup, it would allow for dosages precisely calibrated for each patient, targeting the disease where it lives [source: Human Genome Project Information]. Similarly, pharmaceutical companies could speed up research and development time (and lower costs) by knowing which genes are responsible for a disease and how they react to drugs.
We would also potentially see the end of the trial-and-error technique of prescribing drugs [source: AMA]. Genetic tests would allow doctors to match a condition with the corresponding drug, saving precious time, money and perhaps lives.
2. Gene Therapy
Gene therapy in many ways goes hand-in-hand with genetic disorders; that is, a successful gene therapy requires an understanding of what genetic abnormality (or abnormalities) causes a genetic disorder. The theory goes that genetic disorders, and the genetic abnormalities underlying them, may be cured by repairing or replacing the afflicted bit of the patient's genome. Disease-fighting genes may also be introduced, or a malfunctioning gene may be deactivated.
As of yet, gene therapy remains an experimental and somewhat controversial field. No particular therapy is in wide use, and some patients have died after accepting experimental treatments -- although, admittedly, some of these same patients were undergoing treatment for life-threatening diseases. One common problem is that the body's defenses often attack newly introduced DNA as a pathogen [source: Human Genome Project Information]. Therapeutic genes must also be engineered to be able to integrate into existing DNA, survive cell division and respond to multifactorial disorders. (The latter group of disorders often have a number of disparate causes, further complicating the issue.)
A person's lifespan is certainly affected by environmental factors -- a severe car crash can be fatal, no matter what your genome has to say about it. But in recent years, several studies have shown that various genes may be responsible for regulating aging, immunity and other factors related to longevity.
For example, in 2009, a study at the Tokyo University of Agriculture found that a specific gene that was activated in men but not women appeared to account for why women, on average, live longer than men. The researchers posited that the gene allowed males to develop stronger and larger bodies but at the cost of a longer lifespan [source: BBC News].
In April 2010, researchers affiliated with the University of Birmingham, in the U.K., found that worms with more active forms of a gene known as DAF-16 lived longer, while also showing better resistance to disease and stress [source: ScienceDaily].
Taken as a whole, these studies and others like them show that lifespan -- and some of the factors that inform it, such as immunity -- may have a strong basis in one's genetic makeup, although it is likely affected by a number of genes.
For more on what our genes can tell us, peruse the links on the following page.
Lots More Information
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- Ultimate Gene Quiz
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- Genetically Modified Food Products Quiz
- Aleccia, JoNel. "Who's your daddy? Answers at the drugstore." May 23, 2008. http://www.msnbc.msn.com/id/23814032/#
- American Medical Association. "Pharmacogenomics." http://www.ama-assn.org/ama/pub/physician-resources/medical-science/genetics-molecular-medicine/current-topics/pharmacogenomics.shtml
- American Pregnancy Association. "Paternity Testing." http://www.americanpregnancy.org/prenataltesting/paternitytesting.html
- Ancestry.com. "Genetic Genealogy Questions." http://dna.ancestry.com/faq.aspx;jsessionid=DC619A895D458461013177AF4567A24B.dna03
- BBC News. "Men's genes 'may limit lifespan.'" Dec. 2, 2009. http://news.bbc.co.uk/2/hi/8390055.stm
- Better Health Channel. "Genes and genetics - inheritance." March 2009. http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Genes_and_genetics_inheritance
- Bettinger, Blaine. "Genetic Genealogy Advice for Newbies, Part I." The Genetic Genealogist. April 12, 2007. http://www.thegeneticgenealogist.com/2007/04/12/genetic-genealogy-advice-for-newbies-part-i/
- Biotechnology and Biological Sciences Research Council. "Aging Gene Found to Govern Lifespan, Immunity and Resilience." ScienceDaily. April 2, 2010. http://www.sciencedaily.com/releases/2010/04/100401173728.htm
- Chinnery, Patrick F. "Mitochondrial Disorders Overview." National Institute of Health. Feb. 21, 2006. http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene