RNA

• RNA (ribonucleic acid) is a type of nucleic acid that is involved in the synthesis of proteins and the regulation of gene expression.
• RNA is similar in structure to DNA (deoxyribonucleic acid) but has several important differences that allow it to perform its unique functions.
• RNA is composed of nucleotides, which are the building blocks of nucleic acids.
• Each nucleotide consists of a sugar molecule (ribose in RNA), a nitrogenous base (adenine, guanine, cytosine, or uracil), and a phosphate group.
• Unlike DNA, which is double-stranded, RNA is typically single-stranded, although it can form complex secondary and tertiary structures through base pairing interactions within the same molecule or with other molecules.
• The nitrogenous bases in RNA can form complementary base pairs with each other through hydrogen bonding.
• Adenine (A) pairs with uracil (U), and guanine (G) pairs with cytosine (C).
• RNA can form a variety of secondary structures, including hairpin loops, bulges, internal loops, and stem.
• Some RNA molecules can form complex three-dimensional structures through interactions between distant parts of the molecule.
• In RNA, the nucleotides are joined together by a covalent bond between the 3' hydroxyl group of one nucleotide and the 5' phosphate group of the next nucleotide.
• The base pairing interactions in RNA are weaker than in DNA because RNA uses ribose as its sugar instead of deoxyribose, which lacks a hydroxyl (-OH) group at the 2' position.
• The presence of this -OH group in RNA makes the sugar more reactive and less stable than deoxyribose.
• A forms two hydrogen bonds with U and G forms three hydrogen bonds with C.
• RNA synthesis, also known as transcription, begins with the binding of an enzyme called RNA polymerase to a DNA template strand at a specific sequence called the promoter.
• The promoter sequence is located upstream of the gene or sequence to be transcribed.
• Once RNA polymerase is bound to the DNA template, it unwinds the double helix and starts to synthesise a complementary RNA strand by adding nucleotides one at a time in the 5' to 3' direction.
• The RNA molecule grows in length as RNA polymerase moves along the template strand.
• RNA polymerase continues to add nucleotides until it reaches a termination sequence that signals the end of the transcription process.
• At this point, the newly synthesised RNA molecule is released from the DNA template and RNA polymerase dissociates from the DNA.
• The newly synthesised RNA molecule is not immediately functional, and it needs to undergo several processing steps before it can be used by the cell.
• In eukaryotic cells, for example, the RNA molecule undergoes capping, splicing, and polyadenylation, which involves the addition of a 5' cap, removal of introns, and addition of a poly(A) tail, respectively.
• In eukaryotic cells, a modified nucleotide called the 5' cap is added to the 5' end of the RNA molecule.
• RNA molecules can undergo a variety of chemical modifications to their bases, including methylation, pseudouridylation, and deamination.
• The cap protects the RNA from degradation and helps it to be recognised by the ribosome during translation.
• Splicing involves the removal of introns and the joining of exons.
• Eukaryotic mRNAs typically contain a string of adenine nucleotides, called the poly(A) tail, at their 3' end.
• The poly(A) tail protects the mRNA from degradation and is involved in the export of the mRNA from the nucleus.
• Eukaryotic genes often contain non-coding regions called introns, which are removed from the pre-mRNA by a process called splicing.