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Nucleic Acids
Nucleic acids are biological macromolecules that store, transmit, and express genetic information in living organisms. They play a fundamental role in heredity, as well as in the synthesis of proteins. There are two main types of nucleic acids:
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Deoxyribonucleic Acid (DNA):
- DNA is the genetic material found in the nuclei of cells and some organelles.
- It consists of two polynucleotide chains twisted around each other to form a double helix structure.
- Each polynucleotide chain is made up of nucleotides, which consist of a sugar molecule called deoxyribose, a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
- The nucleotides are connected by phosphodiester bonds between the sugar and phosphate groups, forming a backbone for the DNA molecule.
- The two polynucleotide chains are held together by hydrogen bonds between complementary base pairs: A with T, and C with G.
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Ribonucleic Acid (RNA):
- RNA is involved in various cellular processes, including protein synthesis and regulation of gene expression.
- It is single-stranded and can fold into complex three-dimensional structures.
- RNA also consists of nucleotides, but it contains the sugar ribose instead of deoxyribose.
- The nitrogenous bases in RNA include adenine (A), uracil (U), cytosine (C), and guanine (G).
- RNA molecules can have different types, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), each with specific functions.
Schematic diagram of DNA and RNA: DNA is double
Key features of nucleic acids include:
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Genetic Information: Nucleic acids encode and transmit genetic information from one generation to the next. DNA carries the genetic instructions required for the development, growth, and functioning of living organisms.
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Base Pairing: Nucleic acids exhibit complementary base pairing. In DNA, adenine pairs with thymine, and cytosine pairs with guanine through hydrogen bonding. In RNA, adenine pairs with uracil.
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Replication: DNA undergoes replication, a process where the DNA molecule is duplicated to produce two identical copies. This ensures the faithful transmission of genetic information during cell division.
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Transcription: DNA serves as a template for the synthesis of RNA in a process called transcription. Transcription involves the synthesis of a complementary RNA molecule based on the DNA template.
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Translation: mRNA carries the genetic information from DNA to the ribosomes, where it is translated into proteins. During translation, tRNA molecules bring the correct amino acids to the ribosomes, allowing the assembly of proteins based on the mRNA sequence.