Word: rna
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...invader is tiny, about one sixteen-thousandth the size of the head of a pin. It consists basically of a double-layered shell or envelope full of proteins, surrounding a bit of ribonucleic acid (RNA), the single-stranded genetic molecule, and often enters the bloodstream of its victim after sexual contact. It is an AIDS virus, and its intrusion does not go unnoticed. Scouts of the body's immune system, large cells called macrophages, sense the presence of the diminutive foreigner and promptly alert the immune system. It begins to mobilize an array of cells that, among other things, produce...
...that cell, it finds a receptor into which one of its envelope proteins fits perfectly, like a key into a lock. Docking with the cell, the virus penetrates the cell membrane and is stripped of its protective shell in the process. Within half an hour, the strand of RNA and an enzyme the virus carries with it are floating in the cytoplasm, the fluid interior of the cell...
...remarkable transformation takes place. With the help of the enzyme, the naked AIDS virus converts its RNA into double-stranded deoxyribonucleic acid (DNA), the master molecule of life. The molecule then penetrates the cell nucleus, inserts itself into a chromosome and takes over part of the cellular machinery, directing it to produce more AIDS viruses. Eventually, overcome by its alien product, the cell swells and dies, releasing a flood of new viruses to attack other cells, including more helper T cells and macrophages. The immune system, deprived of a crucial number of those vital T cells, is unable to direct...
...invade a cell, the DNA takes over the cell's genetic machinery and orders it to produce copies of the virus, which escape to infect other cells. The victim cell is often killed in the process. But the AIDS virus is a so-called retrovirus and contains single-stranded RNA. Alone, RNA lacks the ability to conquer cells, but retroviruses carry an enzyme called reverse transcriptase. When the AIDS virus invades an immune-system T cell, the enzyme enables the viral RNA to convert to DNA, take over the cell's machinery, produce copies of itself and disable the cell...
...Peter K Sorger '84, $1500, for his senior thesis entitled "The Self-Assembly of Tarnip Crinkle Virus, an Icosahedral RNA Virus," Professor Stephen C Harrison...