DK Science & Technology: Genetics
Genetics is the study of how living things pass their features from one generation to the next. Your sex and your chances of developing certain diseases are fixed by your genes.
The genetic code has four letters, A, T, C, and G. These letters represent groups of atoms called bases, spaced out along the DNA molecule. The makeup of living things is fixed by the order of these bases. Words in the code are three letters, such as TCA. Genes are like long sentences written with these words.
A genome is the sequence of all the letters of the genetic code in the DNA of a particular organism. The HUMAN GENOME has about three billion letters. Scientists have developed special techniques for sequencing (reading) DNA, with the help of powerful computers.
In 1953, inspired by scientist Rosalind Franklin, Crick and Watson built a DNA double helix (spiral) model. They linked the strands of the helix with A, T, C, and G molecules.
The aim of the Human Genome Project is to produce the complete sequence of the genome of the human being.
Scientists are using results of the Human Genome Project to study genetic diseases (those that may be inherited), such as cystic fibrosis. By identifying the gene, they should be able to diagnose a disease much earlier, and design more effective treatments. Knowing part of the genome means that scientists can already identify an individual’s DNA FINGERPRINT.
Except for identical twins, everyone’s DNA is different. By scanning about 10 sections (each about 500 letters long) of your DNA, scientists can create your DNA fingerprint.
The chance of two individuals having the same DNA sequence in 10 scanned sections is incredibly small. If DNA found at a crime scene—in a hair, for example—matches a sample from a suspect to this degree, then it is proved “beyond reasonable doubt” that the hair is the suspect’s.