nucleic acids

• Which elements do nucleotides contain?

  Carbon, hydrogen, nitrogen, oxygen and phosphorous
• What are the two types of nucleic acid?

  DNA and RNA
• What is a nucleic acid?

  A large monomer made up of many nucleotide monomers linked in a chain
• What are the 3 components of DNA and RNA?

  1. Phosphoryl group

  2. Pentose monosaccharide (Deoxyribose in DNA, Ribose in RNA)

  3. An organic, nitrogenous base (ATGC in DNA, AUGC in RNA)
• How are the components in a nucleic acid monomer joined?

  By strong covalent bonds formed via condensation reaction
• What is the difference between ribose and deoxyribose?

  Deoxyribose has 1 less oxygen (4, not 5)
• What part of a nucleic acid is acidic?

  The phosphoryl group, which is also negatively charged (PO4²⁻)
• How is a polynucleotide formed?

  When the phosphoryl group (5th carbon of sugar, aka 5') of one nucleotide and OH group of the 3rd carbon of the adjacent nucleotide's pentose monosaccharide attach via a condensation reaction
• What is the bond between 2 nucleotides called?

  Phosphopdiester bond
• What is the part of a nucleic acid other than the bases called?

  Sugar-phosphate backbone
• What way does each strand of DNA run?

  From 3' to 5
• What does it mean that the strands in DNA are antiparallel?

  The sugar-phosphate backbone of each strand run in opposite directions
• What bonds attract the base pairs of DNA to each other?

  Hydrogen bonds
• How many hydrogen bonds are there between A and T/U bases?

  2
• How many hydrogen bonds are there between G and C bases?

  3
• Which bases are purine?

  Adenine and Guanine
• What are the full names of A,T,G,C and U?

  Adenine, thymine, guanine, cytosine, uracil
• What is the difference between pyrimidine and purine molecules?

  Purines have double carbon ring structures, pyrimidines have single carbon ring structures
• Which bases are pyrimidine?

  Thymine, Cytosine and Uracil
• What is the difference between the bases of DNA and RNA?

  DNA has Thymine, RNA has Uracil
• How do purine and pyrimidine molecules fit together?

  In a complementary fashion
• What does complementary base pairing in DNA ensure about the relative amounts of ATGC?

  There is exactly the same amount of Adenine and Thymine, and likewise for Guanine and Cytosine
• Which enzyme catalyses the unwinding and separation of DNA's two strands?

  DNA Helicase
• How does the DNA molecule unwind?

  DNA Helicase travels along the DNA backbone, catalysing reactions which break the hydrogen bonds between complementary base pairs as it reaches them.
• What happens after the DNA strand has been 'unzipped' in DNA replication?

  Free deoxyribose nucleotides present in the nucleus form hydrogen bonds with their complementary bases.
• What does DNA Polymerase do?

  Causes a phosphodiester bond to form between unjoined deoxyribose nucleotides which have been attracted to the unzipped strand of DNA
• What direction is the only one DNA polymerase works in?

  From the 3' end to the 5' end of the DNA strand
• Why does DNA have to replicate each template strand in opposite directions?

  Because DNA polymerase only runs along a strand in one direction, but DNA only unwinds and unzips in one direction
• Which strand of DNA is the leading strand, and can therefore undergo continuous replication?

  The strand which is unzipped from the 3' end, as DNA polymerase can replicate it continuously as the strands unzip
• What happens to the strand unzipped from the 5' end in DNA replication?

  DNA has to wait until a section has been unzipped, then work back along the strand. This results in DNA being produced in segments called Okizaki Fragements.
• What joins Okizaki Fragments together?

  DNA Ligase
• What is the name of the strand unzipped from the 5' end, and what type of replication does it undergo?

  Called the lagging strand and undergoes discontinuous replication
• How does a mutation occur during DNA replication?

  Because sequences of bases aren't always matched exactly, and an incorrect sequence can occur in a copied strand. These errors are random and spontaneous
• What is semi-conservative replication of DNA?

  The idea that each new DNA molecule contains one parent strand (from the original DNA molecule) and one new strand made up of nucleotides not from the original molecule
• What experiment provided evidence for semi-conservative replication?

  The Meselson-Stahl experiment
• Provide a brief overview of the Meselson-Stahl experiment.

  1. Bacteria were initially grown in heavy nitrogen (¹⁵N), so all bases in their DNA contained only heavy nitrogen, leaving a band of heavy DNA near the bottom of a test tube

  2. Then, bacteria were grown in normal (¹⁴N) nitrogen. The 1st generation of DNA all had a medium weight, as one strand was heavy and one light, so there was a band of DNA near the middle of the test tube.

  3. Another generation of bacteria was grown in ¹⁴N nitrogen, producing DNA which was 1/2 lightweight (2 light strands) and 1/2 midweight (1 light 1 heavy), meaning that 2 bands formed in the test tube (1 at the top and 1 in the middle)
• What is a gene?

  A section of DNA used to encode a protein
• What do genes control?

  All metabolic processes
• What is a gene locus?


  The position each gene occupies on a chromosome
• What is the proper name for a triplet of three bases?

  Codon