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Radioactive sulfur-35 was used to label the protein sections of the T2 phage, because sulfur is contained in protein but not DNA. [ 6 ] Hershey and Chase inserted the radioactive elements in the bacteriophages by adding the isotopes to separate media within which bacteria were allowed to grow for 4 hours before bacteriophage introduction.
Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1] Phosphorus and sulfur are also common essential elements, essential to the structure of nucleic acids and amino acids, respectively.
The two main classes of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). If the sugar is ribose, the polymer is RNA; if the sugar is deoxyribose, a variant of ribose, the polymer is DNA. Nucleic acids are chemical compounds that are found in nature. They carry information in cells and make up genetic material.
At the time, "yeast nucleic acid" (RNA) was thought to occur only in plants, while "thymus nucleic acid" (DNA) only in animals. The latter was thought to be a tetramer, with the function of buffering cellular pH. [199] [200] In 1937, William Astbury produced the first X-ray diffraction patterns that showed that DNA had a regular structure. [201]
The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the azoles. Thiazoles and isothiazoles contain a sulfur and a nitrogen atom in the ring. Dithioles have two sulfur atoms. A large group of 5-membered ring compounds with three or more heteroatoms also exists.
This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.
Structural elements of common nucleic acid constituents. Because they contain at least one phosphate group, the compounds marked nucleoside monophosphate, nucleoside diphosphate and nucleoside triphosphate are all nucleotides (not phosphate-lacking nucleosides). The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA
Without the phosphate group, the composition of the nucleobase and sugar is known as a nucleoside. The interchangeable nitrogenous nucleobases are derived from two parent compounds, purine and pyrimidine. Nucleotides are heterocyclic compounds, that is, they contain at least two different chemical elements as members of its rings. [citation needed]