nucleic acids

• The monomers of nucleic acids are Nucleotides which consist of three components: Pentose sugar, Organic base, and Phosphate group.
• The two types of organic bases are Purine and pyrimidine.
• Purines are a class of organic bases with a double ring structure and include adenine (A) and guanine (G).
• The polypeptide is further modified by adding carbohydrates, lipids or phosphates.
• DNA can be purified by precipitation, which involves adding ethanol and a salt to an aqueous solution, centrifuging to obtain a pellet of nucleic acid, washing the pellet with ethanol and centrifuging again.
• Different polypeptides may be combined.
• Pyrimidines are a class of organic bases with a single ring structure and include cytosine (C), thymine (T), and uracil (U).
• The structure of a DNA nucleotide consists of Deoxyribose, Organic base (A, T, C or G), and Phosphate group.
• The structure of an RNA nucleotide consists of Ribose, Organic base (A, U, C or G), and Phosphate group.
• The structure of an ATP nucleotide consists of Ribose, Adenine, and three phosphate groups.
• An endergonic reaction is a non-spontaneous reaction that requires an input of energy, for example, ATP formation.
• An intron is a non-coding sequence of DNA that is found between exons.
• Each base in a sequence is read once and is only part of one triplet.
• The genetic code is universal as the same codons code for the same amino acids in almost all organisms.
• Eukaryotic genes are discontinuous with non-coding introns and coding exons.
• A specific sequence of three nucleotides (known as a codon) on a molecule of DNA or RNA codes for a particular amino acid in protein synthesis.
• The genetic code is degenerate, universal and non-overlapping.
• An exon is a region of DNA that codes for an amino acid sequence.
• Protein synthesis is the formation of proteins from amino acids, with two stages: transcription and translation.
• More than one triplet can code for a particular amino acid.
• Prokaryotic genes are continuous with coding sequences only.
• The genetic code is the rules by which triplets in a DNA base sequence code for the sequence of amino acids in a polypeptide chain.
• Free RNA nucleotides align next to their complementary bases during transcription.
• Amino acids carried on adjacent tRNA molecules are joined to form a polypeptide chain during translation.
• RNA polymerase binds to promoter region on a gene during transcription.
• RNA polymerase joins adjacent RNA nucleotides, forming phosphodiester bonds during transcription.
• Translation is the second stage of protein synthesis and takes place in the ribosomes.
• mRNA is used as a template for the attachment of tRNA molecules with complementary anticodons during translation.
• Transcription is the first stage of protein synthesis and involves the formation of pre-mRNA in eukaryotes and mRNA in prokaryotes from a section of the template strand of DNA.
• Post-transcriptional modification, such as splicing, removes introns from pre-mRNA in eukaryotic cells.
• The 'one gene - one polypeptide' hypothesis states that each gene encodes a single protein.
• Antisense strand acts as a template during transcription.
• DNA helicase unwinds section of DNA, breaking hydrogen bonds between the DNA strands.
• RNA polymerase reaches stop codon and detaches, resulting in mRNA.
• Semi-conservative replication is the replication of DNA to produce two new DNA molecules which both contain one new strand and one old strand from the original DNA molecule.
• The structure of rRNA consists of 1800 to 5000 nucleotides, two subunits: one large, one small.
• The function of rRNA is to associate with proteins in the cytoplasm to form ribosomes.
• Ribosomal RNA (rRNA) associates with proteins in the cytoplasm to form ribosomes.
• Transfer RNA (tRNA) carries specific amino acids to the ribosomes.
• DNA helicase catalyses the unzipping of double-stranded DNA into two single strands, each of which acts as a template during semi-conservative replication.