5.9. Molecular Biology: DNA and RNA: Gene Expression

Molecular Biology is an area of ​​science that studies life processes at their most fundamental level, that is, how the molecules inside a cell interact and behave. DNA and RNA are two types of molecules that play a vital role in gene expression, which is the process by which the information in a gene is used to make a functional protein. This topic is essential for understanding genetics and is often covered in detail in ENEM.

DNA (deoxyribonucleic acid) is the molecule that contains the genetic information of an organism. It is made up of two strands of nucleotides that wrap around each other to form a double helix structure. Each nucleotide is composed of a nitrogenous base (adenine, thymine, cytosine or guanine), a sugar (deoxyribose) and a phosphate group. The sequence of these nitrogenous bases is what determines genetic information.

RNA (ribonucleic acid) is similar to DNA, but has some important differences. It is usually single chain, contains the sugar ribose instead of deoxyribose and the base uracil instead of thymine. There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA), each with different roles in the gene expression process.

Gene expression occurs in two main steps: transcription and translation. In transcription, information in a gene is copied from DNA to messenger RNA. This process takes place in the nucleus of the cell and is carried out by an enzyme called RNA polymerase. RNA polymerase binds to the DNA in the gene region and separates the two strands of DNA. It then uses one of the DNA strands as a template to synthesize a complementary mRNA molecule.

Once the mRNA molecule is complete, it is exported from the nucleus to the cytoplasm of the cell, where translation takes place. In translation, the information in the mRNA is used to build a protein. This process is carried out by ribosomes, which read the sequence of bases in the mRNA and add the corresponding amino acids to form the protein chain. tRNA plays a crucial role in this process as it is responsible for bringing the correct amino acid to the ribosome based on the mRNA sequence.

Gene expression is a complex and highly regulated process. Many factors can influence gene expression, including the availability of nutrients, the presence of external signals, and the activity of other proteins in the cell. Furthermore, errors in gene expression can lead to a variety of diseases, including cancer and genetic diseases.

Understanding molecular biology and gene expression is critical to understanding life at its most basic level. This knowledge is not only important for biology, but also has applications in medicine, agriculture and biotechnology. Therefore, it is essential that students preparing for ENEM have a solid understanding of these concepts.

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