Nucleotides are the monomers of nucleic acids; nucleic acids are polynucleotides joined by a condensation reaction that maintains a consistent structural polarity throughout the molecule. DNA consists of two anti-parallel strands with bases that interact via hydrogen bond formation and hydrophobic interactions . In the case of RNA, it is said to have secondary structure (much like amino acid chains) as it folds in on itself and interact via base pairing of different nucleotide residues in the chain. Nucleosides contain only the base and sugar parts - No phosphate Purines are two rings, Adenine and Guanine. Pyrimidines are one ring, Cytosine and Thymine. AT form two hydrogen bonds, CG form three hydrogen bonds • Explain the role of hydrogen bonds in generating secondary structure of RNA. Hydrogen bonds are not the only factors holding the bases together. They are also held together by hydrophobic interactions In the case of RNA, it is said to have secondary structure as it folds in on itself and interact via base pairing of different nucleotide residues in the chain. RNA molecules are also able to form base pairs. These are usually formed within a single strand to form 'double-stranded' loops. The ability to form loops depends on the base sequence of the RNA and is not the same in all parts of the molecule. These structures stabilized by base pairing
are also referred to as secondary structure. Also in a similar way to protein folding, we refer to the 3-dimensional conformation of the RNA molecule as the tertiary structure. Topic 3 Chromatin and Chromosomes • Analytically describe chromatin structure. Explain how proteins and DNA interact to form chromosomes, starting with the 2nm naked DNA molecule. In eukaryotes, DNA occurs as a complex with proteins known as chromatin . Chromatin consists of DNA and two classes of proteins, known as histones and non-histone chromatin proteins. Histones are a set of basic proteins (i.e. they have positive charges due to basic amino acid residue side chains) that interact strongly with DNA. There are five types of histones that work together with the DNA to produce chromatin.