1 Chronic bronchitis: A form of COPD characterized by a chronic productive cough. 2  Emphysema: Lung damage allows air to be trapped in the lungs in this form of COPD. 3  Difficulty blowing air out is its hallmark. 4  Acute bronchitis: A sudden infection of the airways, usually by a virus.
There are only 46 DNA molecules ( 23 pairs) in human somatic cell. There are about 22000 genes and close to 3.2 billion base pairs in total.
DNA (2â²-deoxyribonucleic acid) is the molecular store of genetic information in nearly all living systems. It is a large polymeric molecule composed of monomers known as nucleotides. Each nucleotide consists of a heterocyclic base, a pentose sugar (2â²-deoxy-d-ribofuranose), and a phosphate group. There are four heterocyclic bases in DNA: adenine (A), guanine (G), cytosine (C) and thymine (T). Their structures and numbering system are shown in Figure 1.