5.4. Molecular Biology: DNA and RNA: Transcription of DNA to RNA

Molecular Biology is a branch of science that studies the structure and function of molecules that are essential for life. She is responsible for understanding how different cellular systems interact in terms of DNA, RNA, and protein synthesis, which are the main focuses of this chapter.

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are two key molecules in molecular biology. DNA is the molecule that stores the genetic information of an organism. It is composed of two chains of nucleotides, which are joined by hydrogen bonds to form a double helix structure. Each nucleotide consists of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine).

RNA, on the other hand, is a single-stranded molecule that plays multiple roles in encoding, decoding, regulating, and expressing genes. There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). Each of them has a specific role in protein synthesis.

Transcription is the process by which genetic information stored in DNA is copied into RNA. This process is carried out by an enzyme called RNA polymerase, which binds to a specific region of the DNA called the promoter and separates the two strands of DNA. RNA polymerase then adds complementary RNA nucleotides to the DNA strand, forming an RNA molecule. This process continues until the RNA polymerase reaches a termination sequence, where it detaches from the DNA and releases the newly formed RNA molecule.

There are some notable differences between transcription in prokaryotes and eukaryotes. In prokaryotes, transcription and translation (the process of protein synthesis) occur simultaneously, since there is no nucleus to separate the processes. In eukaryotes, transcription takes place in the nucleus, and the resulting RNA molecule is then processed and transported to the cytoplasm, where translation takes place.

After transcription, RNA needs to be processed before it can be translated into proteins. This process involves adding a 5' cap and a 3' poly-A tail to the RNA molecule, as well as removing non-coding RNA sequences called introns. The resulting RNA, now called messenger RNA (mRNA), is then transported out of the nucleus and into the cytoplasm, where it will be translated into proteins.

In summary, molecular biology is a fascinating area of ​​science that allows us to understand the fundamental processes of life at the molecular level. DNA and RNA play vital roles in these processes, allowing the transcription and translation of genetic information into proteins. Understanding these processes is fundamental to understanding biology and genetics, and is essential for preparing for the ENEM test.

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