American student, David - not his real name - explains why he chooses to buy illegal drugs on the so-called 'dark web'. You don't have to go in front of a street dealer, where there might be a risk of violence, he adds. And it is not just drugs which are available on this online black market. Fake passports, guns - even child pornography.
Genetic material is that substance which not only controls the inheritance of traits from one generation to the next but is also able to express its effect through the formation and functioning of the traits. Components of genetic material which control characters are called genes. Genes are located over chromosomes. In sexually reproducing organisms, an indiÂ­vidual receives one genome or one set of chromosomes (and hence genes) from male parent and a second genome or set of chromosomes from female parent.
You can view a 3-D rotatable image of DNA here... The hereditary material of all multi-cellular organisms is the famous double helix of deoxyribonucleic acid (DNA). This contains all of our genes. DNA, itself is made up of four chemical bases, pairs of which form the rungs of the twisted, ladder-shaped DNA molecules. These four molecules are adenine (A), thymine (T), cytosine (C), and guanine (G). All genes are made up of stretches of these four bases (arranged in different ways and in different lengths). Photo: National Institute of Health. A critical feature of DNA is the ability of the nucleotides to make specific pairs: .