Translating the code : protein synthesis.

Part 1:compares cells to factories which manufacture all the proteins that an organism needs. It describes the code that directs these cellular factories to produce the right proteins at the right time: from chromosomes to the molecular structure of the DNA and how the discovery of this structure provided the key for unlocking many of the mysteries about how the genetic code operates. Computer graphics clarify the various steps of protein synthesis. The section ends with a discussion of biology's central dogma, which holds that one gene codes for one protein and that genetic information always flows in one direction: from DNA to RNA protein. Part 2: looks at challenges to this central dogma. It describes Nobel Laureate Susuma Tonegawa's solution to the problem of how the body can make more antibody proteins than there are genes. Tonegawa showed that the genes can be rearranged so that they can code for different proteins. Part 2 also shows that retroviruses, such as the AIDS virus, challenge the usual assumption that DNA always codes for RNA. Another Nobel Laureate, Barbara McClintock, further challenged conventional thinking by showing that DNA can be influenced by environmental factors and that proteins can pass