By Charlotte King
Ten years ago the first working draft of the full sequence of the human genome was completed. The international Human Genome Project was started in order to map the location of all genes in human DNA.
Our DNA
A human has 23 pairs of chromosomes that contain all our genes: one in each pair came from the mother and the other from the father. Genes are the code for the structures in the body as well as providing maintenance throughout life. But because there are around 3 billion DNA bases within these chromosomes it was not an easy task to sequence them all.
The Project
The Human Genome Project was started in 1990 by James Watson, who was one of the original discoverers of the helical structure of DNA along with Rosalind Franklin and Francis Crick. The final sequence was composed of a combination of DNA from four men.
The original genome sequencing method, Sanger Sequencing, was pioneered in the 1970s and was the main method used to sequence DNA for 30 years. But new methods have started to emerge and with these new technologies, centres will be able to generate thousands of millions of DNA letters per day, rather than the current 100 million per day. It costs $10,000 a day (£6,505) to have one’s genome sequenced.
The genomes of any two people are always more than 99 per cent the same. This means the sequence of two people’s genomes will be similar, although not identical. The project has involved sequencing different variations (alleles) of the same gene that are located in the same place along the DNA. An example would be different alleles of genes that cause different eye colours.
Pros and cons of DNA sequencing
Once an allele is linked to a disease, it can potentially be tested for in a person’s DNA sample, so a person may discover they are likely to get a disease. Scientists can share what they have found out about genes.
But in the future if it ever becomes standard to have a genome sequenced and checked for diseases, there are many ethical issues. What if one’s genes reveals that they are likely to get 10 diseases – does this mean you should be treated for all of them ‘just in case’?
There are also issues about where information is shared and stored: should your employer and insurance company know, and will this lead to discrimination? What if the information was not securely stored and got into the wrong hands? There are still many questions to answer.
The reality is that we are still in the early stages of interpreting the results from the human genome sequence. Despite the fact the genome was declared to be sequenced already, not all of it is currently sequencable and there is much left to be done in understanding the complete genetic nature of humans – likely never.
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