Q.:There was a big announcement in June that the rough draft of the human genome had been completed. What is different about this new announcement? A.: Last June the scientists said they had copied almost all of the chemical letters of the genome. Many consider this announcement to be more important because the scientists are now able to read the code and are telling us what it says.
Q.:What is the human genome? A.: The complete genetic sequence of all human DNA.
Q.:What is a sequence? A.: A sequence refers to the order of chemical units that make up DNA. Chemical units consist of four nucleic acids adenine, thymine, guanine and cytosine, which form the letters of DNA. Adenine always combines with thymine and guanine with cytosine. Such a bonding is a base pair, which is what is sequenced.
Q.:How many sequences are there in the human genome? A.: Three billion. But only 1.1 to 1.4 percent of the sequences are used to make active genes. Scientists still are not sure what the remaining sequences do, but the vast majority of them are silent, they do not code for anything.
Q.:How do they search for sequences? A.: High speed computers and software programs run through the sequences to identify genes and noncoding base pairs.
Q.:What is the most unexpected new finding? A.: That the human genome has far fewer genes than anyone thought, about 30,000 instead of the expected 100,000.
Q.:Why are there two competing teams sequencing the genome? A.: The U.S. government launched Human Genome Project in 1990. It was expected to cost $3 billion and be completed by 2005. But a private company, Celera Genomics, announced it would start sequencing in 1998, beginning a furious race.
Q.:What impact did that have? A.: It speeded up completion of the sequencing by nearly 4 years.
Q.:What effect will knowing the human genome have on our health? A.: It is expected to revolutionize medicine, first by letting you know what diseases you may be susceptible to and how you might avoid them, and secondly, by enabling pharmaceutical companies to create thousands of new drugs.