DNA211 - DNA Structure and Replication - 1 DNA is the...

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DNA Structure and Replication - 1 DNA is the genetic molecule of all life. DNA (along with associated proteins) is found in chromosomes. DNA ultimately controls all cell activities. As studied, specific enzymes catalyze the metabolic activities of cells. The instructions for the synthesis of enzymes (and all proteins), as well as RNA molecules (see later) are found in the structure of DNA. We also know that the DNA in each of our cells is identical; DNA molecules duplicate* prior to cell division ensuring that the new cells formed are genetically identical to the original cell. *Duplicate and replicate are both commonly used for the same process. We know, too, that genes, or our inheritable traits, are functional regions of DNA. A gene locus of DNA stores the information that specifies the sequence of amino acids that form a specific polypeptide. The genes, or more precisely, alleles we inherit from our parents determine the polypeptides we synthesize in our cells, which determine the structure and functioning of our cells and tissues. What DNA is and how DNA works is the subject of this section. We will look at the structure and functions of DNA, how the information stored in DNA is used to direct cell activities and how cells regulate the activity of their genetic molecules. We shall also see how DNA duplicates itself prior to cell division. The search for the molecule of inheritance spanned a century from the 1850's to 1953, when Francis Crick and James Watson announced they had a model for the three dimensional structure of DNA. Genetic Material is in the Nucleus DNA was first isolated by Friedrich Miescher in 1868. Miescher identified a phosphorus containing acid in the nuclei of cells that he called nuclein. He also found a basic protein portion in the nucleus, which we today know are the histone proteins. In 1914 Robert Feulgen developed a stain that was selective for this acid material in the nucleus. Feulgen noted that the stained volume of the nuclear material was the same for all body (somatic) cells, but gametes had half as much of this material. He also noted that cells that were about to divide had twice as much nuclear material. He also noted that different species had different volumes of the stained nuclear materials. By the early 1900's the search for the genetic molecule was focused on molecules found in the nucleus, particularly after Morgan's work confirming that genes were on chromosomes. However, it was not until the 1930's when Hammerling did a set of experiments using an alga, Acetabularia , that we confirmed that the information needed to express genetic traits was located in the nucleus. is a single-celled organism, with several morphologically different species, that is large (5cm) and has three morphologically distinct regions – a cap, a stalk and a base. The nucleus is in the base.
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DNA211 - DNA Structure and Replication - 1 DNA is the...

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