Overview of Biological Information Metabolism

Before the middle of the nineteenth century, our understanding of heredity was fuzzy and mostly wrong. The first scientific advances were the studies of an Austrian monk named Gregor Mendel. He found that inheritance of traits could be explained by segregation [local], and he found that some genes are dominant, whereas others were recessive (dominant and recessive). Mendel's Laws [local] form the basis for the field of genetics. You may want to refresh your knowledge of the vocabulary [local] associated with genetics.

Here is a practical test of your understanding of genetics. This site will permit you to cross two varieties of pea, just as Mendel did. There are two alleles for seed color (Y is dominant for yellow; y is recessive and will produce green seeds in the homozygous condition) and shape (R is dominant for round seeds and r is recessive and will produce wrinkled seeds when homozygous). See how few steps it will take you to produce a population of seeds that are all breeding true for yellow/round seeds (YY/RR). How few steps will it take to breed a population of true breeding green/wrinkled seeds (yy/rr)?

The first half of the twentieth century was a busy time for genetics. The concept of genes gained credence and the notion that these were somehow contained in the nucleus of eukaryotic cells. In the early 1940's, Beadle and Tatum demonstrated that mutations in single genes caused defects in single enzymes, leading to the "One Gene-One Enzyme Hypothesis" [local], the convergence of genetics with biochemistry. At about the same time, transformation of bacteria with fractionated cellular materials let to the demonstration of DNA as hereditary material. Within a decade, X-ray diffraction data was used by Watson and Crick to elucidate the structure of DNA.

The elucidation of the structure of DNA initiated the era of molecular biology and the gradual elucidation of the molecular mechanisms underlying information metabolism. Within a decade, Francis Crick proposed the Central Dogma of Molecular Biology. This stated that DNA is used as a template to replicate new DNA polymers, and that information flows unidirectionally from DNA ---> RNA ---> Protein. [Although we have had to since modify the Central Dogma to accommodate the flow of information from RNA ---> DNA in retroviruses such as the hiv virus that causes AIDS, it still provides the overview for an understanding of cellular information metabolism.]

Here is a tutorial on DNA and heredity. If you have little background in biology you would be well advised to work through this tutorial. Try to understand the basic concepts of genetics and become more aware of the vocabulary specific to this area of science.

Here is a hypertext chapter that will provide an overview of the individual processes comprising the Central Dogma of Molecular Biology. It is suggested that you read it now for the overview, but refer to it again during this course when you have difficulties with some of the details that it covers.