Nucleotides

• Name the bond that joins nucleotides into a polynucleotide

  Phosphodiester
• explain how the organic bases help stabilise the structure of DNA

  Hydrogen bonds between the complimentary pairs hold the two strands together; many hydrogen bonds provide strength;
• explain how the structure of DNA is related to its function

  DNA is double stranded with a sugar-phosphate backbone to provide strength and stability; Its a large molecule to store lots of information; Its in a helix so it is compact; the base sequence allows proteins to be coded for; Its double stranded so it allows semi-conservative replication; There are weak hydrogen bonds to allow for breaking during replication;
• how do you find out the percentage of bases in DNA

  All the bases will add up to 100%. Complimentary pairs will have the same frequency as each other in a double strand. They may have different frequencies in a single strand.
• compare and contrast DNA and RNA

  DNA is a large molecule, whereas RNA is a smaller molecule; DNA contains Thymine, whereas RNA contains Uracil; DNA contains Deoxyribose sugar, whereas RNA contains Ribose sugar; Both composed of polymers of nucleotides; both contain phosphodiester bonds; both involved in protein synthesis; DNA stays in the nucleus, whereas RNA leaves the nucleus;
• describe how the arrangement of prokaryotic DNA is different from eukaryotic DNA

  Prokaryotic is circular, not linear; Prokaryotic is not associated with histones, eukaryotic is associated with histones; prokaryotes only have 1 piece of DNA plus plasmids, eukaryotes have many/multiple strands of DNA;
• describe the structure of the DNA double helix

  It is made of 2 strands of polynucleotides that run antiparallel; there are 4 different bases that pair through hydrogen bonding with their complimentary pair; cytosine to guanine, and adenine to thymine;

  The DNA is coiled in a helix;
• why did many scientists doubt DNA carried the genetic code

  It is a relatively simple molecule with only four different bases.