Nucleolus ribonucleic acids

That the cytoplasmic nucleic acid is present in the mitochondria, the micro-eomes, and the non-sedimentable cell-sap is also known.117 The nuclear ribonucleic acid has been reported to be associated with the nucleolus and the chromosomes.118 It is known, moreover, that the ribonucleic acids of the different parts of the cell are biochemically distinct, since they become labeled with P32 at different rates.119 In liver cells, the nuclear ribonucleic acid is also chemically distinct from the cytoplasmic material, since the two differ in composition.120 It is clear, therefore, that ribonucleic acids prepared from whole cells are likely to be mixtures of various molecular species. 

The nucleus stores the cell s genetic information as DNA in chromosomes. It is bounded by a double membrane but pores in this membrane allow molecules to move in and out of the nucleus. The nucleolus within the nucleus is the site of ribosomal ribonucleic acid (rRNA) synthesis. 

The nucleus of eukaryotic cells is a very complex structure, containing various components. It is separated from the rest of the cell by two membranes named the nuclear envelope. At regular intervals, the two membranes of the nuclear envelope form pores with a diameter of around 90 nm. These pores regulate flux of macromolecules to and from the cytoplasm. Inside the nucleus is located the nucleolus, which acts to produce ribonucleic acid (RNA), which is the first step for ribosome synthesis. 

The cell body contains many structures of importance. The nucleus is usually located in the center of the cell body. It contains widely dispersed, fine chromatin material. The chromatin is composed of deoxyribonucleic acid (DNA) and its associated histone proteins. The nucleolus contains the specific portion of DNA encoding the ribonucleic acid (RNA) of future ribosomes. 

The nucleus of the cell (Figure 1.2) is composed of a porous nuclear membrane, the nucleolus, and soluble materials. The nucleolus contains ribonucleic acids (RNA) and genetic materials also termed chromatin that code for the proteins synthesized upon the ribosomes in the cell cytoplasm. The nuclear membrane is continuous with the outer membrane of the endoplasmic reticulum. Messenger RNA synthesized in the nucleus is transported across the nuclear membrane and is involved in protein synthesis. It fits into the groove between the large and small rRNA subunits (Figure 1.2)... 

At first, information on the chemical composition of the nucleoli was obtained by histochemical methods. For example, the treatment of such fixed preparations with ribonuclease demonstrated that ribonucleic acid is an important component of the nucleolus. Vincent and Baltus [15] made major contributions to our knowledge of the chemical composition of nucleoli when they isolated the structure from both the mature starfish and ungerminated embryos. The nucleolus of the starfish embryonic cell is so big that the experimenter need only disrupt the cell in appropriate media, usually isotonic sucrose, and then centrifuge the preparation by a process of differential centrifugation to sediment a pellet composed mainly of nucleoli. 

Errera, M., Hell, A., Perry, R.P. The role of the nucleolus in ribonucleic acid and protein synthesis. II. Amino acid incorporation into normal and nucleolar inactivated HeLa cells. Biochim. biophys. Acta (Amst.) 49, 58-63 (1961)... 

Nucleoproteins consist of basic proteins in saltlike linkages with nucleic acids (Chapter VIII). Because nucleoproteins are probably present in all cells and vital to growth, there is tremendous biological interest in the histochemical detection of the nucleic acids. Chromosomes, sperm heads, and certain viruses consist largely of nucleoprotein. Two nucleic acid types occur in plant and animal cells deoxyribonucleic acid (DNA), typically present in the nucleus, and ribonucleic acid (RNA), typically found in the cytoplasm and in the nucleolus (see, however. Chapter VIII). Both contain phosphoric acid groups and purine and pyrimidine bases but differ in the pentose moieties. 

The nucleoproteins of the nuclei of trout, salmon and herring sperm, are made up almost entirely of protamine and desoxyribonucleic acid. The nucleoproteins of thymus are made up of desoxyribonucleic acid (40%), ribonucleic acid (1-2%), histones and non-basic proteins. The cellular nuclei contain chiefly desoxyribonucleic acid but, in addition, there is a little ribonucleic acid (in the nucleolus and chromosomes). The cytoplasmic nucleoproteins in general contain only ribonucleic add assodated with proteins which do not have the basic properties of those joined to desoxyribonucleic acid. But the reproductive cell of animals (oocytes) contain desox5rribonudeic add in the cytoplasm. The desoxyribonucleic add of the chromosomes is combined with histones, protamines, and a protein of the usual t3rpe, which is referred to as residual protein. 

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