October 28, 2010
By Brian Bujdos
Scientists at nine different research facilities located throughout the world have nearly reached their goal to map at least 99 percent of all of the variations in the human genome.
Ironically, it turns out that 99 percent of all human genomes are the same. It is the one percent of the human genome in which these variations take place that makes people different – not only physically, but internally. And it’s the internal part that scientists consider so important, because variations in the human genome make some people more susceptible to diseases like cancer or Alzheimer’s, perhaps even erectile dysfunction. Eventually, scientists say, people will be able to begin preventive treatment for some diseases before the disease becomes apparent.
The worldwide project is called 1000 Genomes, which is a $120 million, five-year project that will end in 2012. So far, researchers have mapped the entire genomes of 79 people of European, West African and East Asian ancestry
Researchers discovered that there are about 15 million places in the human genome where one person’s genetic code is different from another. Scientists were also excited to learn that each person carries an average of 250 to 300 genetic changes that would cause a gene to stop working normally. Approximately 50 to 100 genetic variations are currently known to be involved with inherited diseases. This current research will help to increase that number.
Scientists with the 1000 Genomes project also discovered that there are 60 new mutations per human generation. This was discovered by looking at two families of three members each: mother, father and daughter. Each daughter had about 60 mutations that were not passed down by the parents.
Trying to understand the make-up of the human genome might require a little time in the classroom. Here are the basics: approximately 20,000 to 25,000 genes comprise the human genome. All of these genes are encoded in a chain of about 3.1 billion individual chemicals called bases.
Here’s the way that Medical News Today described the genome in more detail:
”Human DNA comprises four chemical units or "bases": adenine (A), cytosine (C), guanine (G) and thymine (T). Imagine an alphabet with only four letters, and the human genome being a huge instruction manual for creating a person, but written only in this alphabet.
Genetic variations in the instruction manual or genome occur when the ‘bases’ appear in a different order. The variations can be small scale, the equivalent of two different spellings of the same "word" in the same place in the ‘instruction manual,’ or they can be large scale, like a section from one chapter of the manual being taken out and inserted in the middle of a different chapter.”
This is what the researchers have trying to decipher with the 179 complete genomes, as well as the protein-coding genes of 697 additional people. So far, the study has compiled more than 4.5 terabases of DNA sequence (that’s 4.5 million, million base letters) – enough to fill more than 400,000 publications the size of the New York City phone book.
More information can be found at 1000genomes.org or in the current issue of the journal Nature.
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