Dna e rna humano

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  • Publicado : 7 de novembro de 2011
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ibonucleic acid (English pronunciation: /raɪbɵ.njuːˌkleɪ.ɨk ˈæsɪd/), or RNA, is one of the three major macromolecules (along with DNA and proteins) that are essential for all known forms of life.Like DNA, RNA is made up of a long chain of components called nucleotides. Each nucleotide consists of a nucleobase (sometimes called a nitrogenous base), a ribose sugar, and a phosphate group. Thesequence of nucleotides allows RNA to encode genetic information. All cellular organisms use messenger RNA (mRNA) to carry the genetic information that directs the synthesis of proteins. In addition,some viruses use RNA instead of DNA as their genetic material; perhaps a reflection of the suggested key role of RNA in the evolutionary history of life on Earth.[1][2]

Like proteins, some RNAmolecules play an active role in cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is proteinsynthesis, a universal function whereby mRNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, whereribosomal RNA (rRNA) links amino acids together to form proteins. In 2011, it was proved that the methylation of mRNA has a critical role in human energy homeostasis. This opens up the field of RNAepigenetics.[3]

The chemical structure of RNA is very similar to that of DNA, with two differences: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type ofribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine. Uracil and thymine have similar base-pairing properties.

Unlike DNA, most RNA molecules aresingle-stranded. Single-stranded RNA molecules adopt very complex three-dimensional structures, since they are not restricted to the repetitive double-helical form of double-stranded DNA. RNA is made...
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