nucleic acids

• Nucleotides contain a deoxyribose pentose sugar, a nitrogenous nucleotide (A, T, G or C in DNA) (A, U, G, C in RNA), and a phosphate group.
• Nucleotides function to form monomers of nucleic acids, help regulate many metabolic pathways, and may be components of many coenzymes.
• Nucleotides can become phosphorylated nucleotides when they contain more than 1 phosphate group.
• DNA contains 2 polynucleotide strands, which run in opposite directions, making them antiparallel.
• DNA has 2 ends: 5’ (where phosphate group is bonded to 5th carbon on pentose sugar) and 3’ (where phosphate group is bonded to 3rd carbon on pentose sugar).
• DNA has a double helix shape and a phosphodiester bond, which is the covalent bond between sugar residue and phosphate group, are hydrolysed when the polynucleotide is broken down.
• DNA is long, so that it can carry a lot of encoded genetic information.
• DNA contains purines, which contain 2 rings, and pyrimidines, which contain 1 ring.
• A and T are complementary base pairs, forming 2 hydrogen bonds, while G and C are complementary, forming 3 hydrogen bonds.
• DNA is mostly contained in the nucleus of eukaryotic cells, with each large molecule of DNA tightly wound around histone proteins into chromosomes.
• In prokaryotic cells, DNA is looped and naked, not wound on histone proteins and is not enclosed in a nucleus.
• DNA replicates semi-conservatively, with each replicated molecule having 1 old strand and 1 new strand.
• DNA replication involves DNA unwinding, catalysed by gyrase enzyme, and DNA unzipping, as hydrogen bonds between nucleotide bases are broken, catalysed by DNA helicase.
• During DNA replication, free nucleotides in nucleoplasm bond to exposed bases, catalysed by DNA polymerase enzyme, in 5’ to 3’ direction.
• DNA replication also involves the replication of loops of DNA inside mitochondria, chloroplasts and prokaryotes, which involves a bubble sprouting from the loop and unwinding and unzipping, and complementary nucleotides joining to the exposed ones until the whole loop is copied.
• Mutations can occur during DNA replication, but this occurs only once in 10^8 base pairs.
• DNA transcription involves a gene unwinding and unzipping, with hydrogen bonds between complementary bases breaking, forming the template strand, and RNA polymerase catalysing the formation of temporary hydrogen bonds between RNA nucleotides and the gene, forming a coding strand.
• DNA translation involves mRNA passing out of the nucleus and attaching to a ribosome, with tRNA molecules bringing the amino acids and finding their place when the anticodon binds by temporary hydrogen bonds to the complementary codon on the mRNA.
• DNA transcription and translation are semi-conservative processes, with each replicated molecule having 1 old strand and 1 new strand.
• The genetic code is degenerate, meaning multiple base triplets can code for the same amino acid, non-overlapping, meaning DNA is read from a fixed point and in groups of 3, and universal, meaning the same base triplet of DNA bases codes for the same amino acid in most organisms.