DNA

• The Central Dogma of Biology refers to the fundamental principle that explains how genetic information flows within a biological system, from DNA to RNA to protein.
• DNA (Deoxyribonucleic acid) contains the genetic information that is passed on from one generation to another and serves as the blueprint for the production of all proteins in an organism.
• DNA is transcribed into RNA (Ribonucleic acid), which is a copy of a specific section of the DNA molecule and serves as an intermediate step between DNA and protein synthesis.
• RNA is then translated into proteins, which are the building blocks of cells and perform various functions in an organism, including structural support, catalysing chemical reactions, and facilitating communication between cells.
• The sequence of bases in the DNA molecule provides the genetic code that determines the sequence of amino acids in proteins, which are the building blocks of cells.
• DNA (Deoxyribonucleic acid) is a double-stranded, helical molecule that carries the genetic information of an organism.
• The four types of nitrogenous bases found in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T).
• The building blocks of DNA consist of a sugar molecule (deoxyribose), a phosphate group, and these nitrogenous bases.
• A nucleotide is a building block of DNA and RNA, consisting of three components: a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil), a sugar molecule (ribose in RNA or deoxyribose in DNA), and a phosphate group.
• The nitrogenous base is attached to the sugar molecule through an N-glycosidic bond.
• The sugar is attached to the phosphate group through a phosphodiester bond.
• Nucleotides are joined together by covalent bonds between the phosphate group of one nucleotide and the sugar molecule of another, forming the backbone of DNA and RNA.
• In contrast, a nucleoside is a molecule composed of a nitrogenous base and a sugar molecule (ribose or deoxyribose) but without a phosphate group.
• Nucleosides are formed by the removal of the phosphate group from a nucleotide.
• The 5' to 3' directionality is sometimes referred to as the orientation.
• The sugar and phosphate molecules form the sides of the ladder, and the nitrogenous bases pair up in the center.
• The two strands of DNA run in opposite directions (antiparallel) with their ends labeled 3' (three prime) and 5' (five prime) respectively.
• The two strands are held together by hydrogen bonds between the paired bases.
• The sugar molecule in each nucleotide has two distinct ends: a 3' end and a 5' end.
• The 3' end of the sugar molecule has a hydroxyl (-OH) group attached to it, while the 5' end has a phosphate group attached to it.
• In a DNA strand, 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.
• This creates a sugar-phosphate backbone with a specific orientation, where the 5' end of one nucleotide is linked to the 3' end of the previous nucleotide.
• The pairing of bases in DNA is specific and always follows the rule of complementary base pairing: Adenine pairs with Thymine, and Cytosine pairs with Guanine.
• B-DNA is the most common and well-studied conformation of DNA.
• In the B-DNA conformation, the DNA double helix has a right-handed twist, and the base pairs are stacked perpendicular to the axis of the helix.
• A-DNA is a conformation similar to B-DNA, but the helix is more compact and has a wider diameter.
• In the A-DNA conformation, the base pairs are tilted relative to the helix axis, and the helix has a shorter rise per base pair than B-DNA.
• Z-DNA is a left-handed helix that is more elongated than B-DNA or A-DNA.
• Z-DNA is characterised by the formation of a zigzag pattern in the phosphate backbone, which is thought to be caused by the presence of alternating purine and pyrimidine bases in the DNA sequence.
• Sanger sequencing, also known as chain termination sequencing, is a method that uses fluorescently labeled dideoxynucleotides to generate DNA fragments of different lengths.
• The fragments are separated by size using gel electrophoresis, and the sequence is determined by reading the fluorescence signals from the labeled nucleotides.
• Next-generation sequencing (NGS) is a collection of high-throughput sequencing technologies that can generate millions of sequences simultaneously.
• In NGS, DNA is fragmented into smaller pieces and ligated to adapters for amplification and sequencing.
• The sequence data is then analyzed using specialized software to reconstruct the original DNA sequence.
• Cell lysis is the first step in DNA isolation and involves breaking open the cells and releasing the DNA.
• Cell lysis can be achieved by physical methods such as grinding or chemical methods such as using detergents or enzymes to break down the cell membrane and nuclear envelope.
• The goal of cell lysis is to release the DNA into a solution that can be further processed.
• Removal of proteins and other contaminants is the next step in DNA isolation and involves removing proteins, lipids, and other cellular debris that can interfere with the DNA isolation and purification.
• The removal of proteins and other contaminants can be achieved by adding a salt, such as sodium chloride, and a detergent, such as SDS, to the cell lysate, which causes the proteins and other contaminants to precipitate out of solution.
• The DNA remains in solution after the removal of proteins and other contaminants.