Why is an eye cell an eye cell and not a liver cell? How are genes expressed? How does the information stored in DNA eventually translate into an organism? How do we go from DNA out to an organism that is capable of describing it? (Let alone cloning it!) How do the 24000 genes in a human expressed to result in you? Most of the functions of metabolism, such as those in photosynthesis and respiration are regulated by proteins that are coded for by genes. When we say that a gene is 'expressed" we refer to the process where the information in DNA is transcribed to the intermediate information in RNA and then transcribed into the language of proteins. And proteins do all the work in cells; some are structural, like muscle fibers, some are metabolic, like enzymes, others are regulators, like hormones, and still others are defense molecules like those in the immune systems of animals. This lecture looks at how genes are expressed, how genes are regulated, turned on and off, in certain cells or in response to certain cues. Gene expression in tied to development since some genes must be specifically expressed in certain cells, tissues and organs, but off in others. We also introduce the idea that all the DNA in a cell contains all the information for an complete organism, through the dramatic demonstrations in animal cloning.
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