The field of genetics and genomics is advancing at an incredible pace. The completion of the Human Genome Project was just the beginning. Now, thanks to rapid advances in sequencing technology and bioinformatics, we have made significant progress toward sequencing 1000 genomes from around the world, uncovering great genetic diversity and challenging us to understand the biologic relevance. Sequencing the exome (the protein-coding parts of the genome) of a patient with an undiagnosed condition is already a reality. Even beyond human genetics, genomic technologies are making an impact on pulmonary disease, enabling characterization of new respiratory pathogen genomes, such as the SARS virus and pandemic H1N1 influenza, with unprecedented speed. Against this backdrop, a chapter on the genetics of lung diseases could easily be out of date before it is even in print. Thus it does not seek to be encyclopedic, but to give the reader a grounding in the principles of human genetics, an overview of current knowledge in Mendelian lung diseases and a summary of recent progress in understanding genetic factors contributing to common lung conditions. It outlines some of the emerging roles of epigenetic modifications and aims to give a vision of where the field is moving, concluding with current and future prospects for genetically targeted therapies.
Principles of Human Genetics
The term “genome” refers to the genetic make-up of an organism (Table 7-1). Mammalian genomes are composed of deoxyribonucleic acid (DNA) and can be subdivided into a nuclear genome – DNA within the nucleus of each cell – and a separate circular genome housed within each mitochondrion. DNA has a double-helix structure, each strand comprises four constituent bases – adenine (A), cytosine (C), guanine (G), and thymine (T) – that pair together, A with T and G with C. DNA needs to be replicated each time a cell divides. This strict base pairing ensures accurate copying of the DNA code.
Table 7-1Glossary of Genetic Terms ||Download (.pdf) Table 7-1Glossary of Genetic Terms
|Genome ||The complete genetic makeup of an organism, including all coding and noncoding DNA |
|Gene ||A discrete protein-coding unit within the genome. Genes are typically subdivided into exons (blocks of protein-coding DNA), introns (intervening noncoding DNA), and flanking regulatory regions |
|Exome ||The entire sequence of all exons within the genome |
|Somatic ||Relating to any cell of the body other than the germ cells. Mutations in somatic cells cannot be passed on to the next generation |
|Chromosome ||A higher order structure into which DNA is packaged. Humans have 23 pairs of chromosomes, 22 autosomes, and a pair of sex chromosome, X and Y, that determine gender |
|Telomere ||The cap at the ends of each chromosome, composed of hundreds of copies of the repeat sequence TTAGGG |
|Diploid ||Containing a full complement of 23 chromosome pairs. All normal somatic ...|