. Cell heredity. Cytogenetics. MECHANISMS OF GENE ACTION 299 DNA BASE RATIOS AND GENE ACTION The unitary hypothesis of gene action proposes that genes control cellular functions by determining protein specificity, and that this, in turn, is accomplished by the translation of a linear code from the nucleo- tide sequence of DNA to the amino acid sequence of protein. Recent studies of the physical properties of DNA extracted from a large number of different species have provided data not easily reconciled with the unitary hypothesis. A method for determining the density of DNA by equilibrium sedi
. Cell heredity. Cytogenetics. MECHANISMS OF GENE ACTION 299 DNA BASE RATIOS AND GENE ACTION The unitary hypothesis of gene action proposes that genes control cellular functions by determining protein specificity, and that this, in turn, is accomplished by the translation of a linear code from the nucleo- tide sequence of DNA to the amino acid sequence of protein. Recent studies of the physical properties of DNA extracted from a large number of different species have provided data not easily reconciled with the unitary hypothesis. A method for determining the density of DNA by equilibrium sedimen- tation in cesium chloride was described in Chapter 7. When DNA ex- tracts from different organisms were centrifuged by this method, it was discovered that they varied considerably in density. Of the four nitrogen 100 80 - 60 r 40 20 ^M. phlei Serratia- E. coli. Calf thymus Salmon sperm Denatured *Z). pneumoniae AT-DNA Density FIGURE Relationship of density to the guanine-cytosine content of various samples of DNA. The density as determined by equilibrium centrifugation in cesium chloride (see Chapter 7) was correlated with base composition of both native and de- natured samples of the DNA of a number of species (from Doty, Marmur, and Sueoka, 1959, BroofchavenSymp. Biology, 12:10).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sager, Ruth; Ryan, Francis J. (Francis Joseph), 1916-. New York, Wiley
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