Both Ribosomal RNAs Most Transfer RNAs Are Processed From Larger Precursors

In mammalian cells, the three rRNA molecules are transcribed as part of a single large precursor molecule. The precursor is subsequently processed in the nu-cleolus to provide the RNA component for the ribo-some subunits found in the cytoplasm. The rRNA genes are located in the nucleoli of mammalian cells. Hundreds of copies of these genes are present in every cell. This large number of genes is required to synthesize sufficient copies of each type of rRNA to form the 107 ribosomes required for each cell replication. Whereas a single mRNA molecule may be copied into 105 protein molecules, providing a large amplification, the rRNAs are end products. This lack of amplification requires a large number of genes. Similarly, transfer RNAs are often synthesized as precursors, with extra sequences both 5' and 3' of the sequences comprising the mature tRNA. A small fraction of tRNAs even contain introns.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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