A1.2 Molecules - Nucleic Acids

• The universal nature of the genetic code demonstrates all life forms have common ancestry
• Deoxyribose and phosphate makes up the backbone of DNA

  
• The base pair not found in DNA is Uracil – Adenine
• The base pairs are joined to carbon
• The complementary bases are linked by hydrogen bonds
• This is a nucleotide

  
• Nucleotides are held by covalent bonds
• RNA contains the ribose sugar with 1 strand with the bases U,G,C,A
• The two strands of DNA are antiparallel

  
• Molecules are formed when two or more atoms chemically bond together.
• The properties and behavior of molecules are determined by the types and arrangement of atoms within them.
• The polarity in a water molecule is determined by the arrangement of the hydrogen atoms.

  
• Dipeptide: a peptide composed of two amino-acid residues.

  
• Beta-glucose molecule

  
• Nucleic Acids
• Nucleic Acid - A molecule that contains genetic information in the form of nucleotides

  
• A nucleotide structure is a phosphate group, deoxyribose sugar, and a nitrogenous base

  
• Nucleotide Nitrogenous Bases

  
• Bonding in Nucleic Acids: Sugar-Phosphate Backbone

  
•  The primary genetic material found in living organisms: DNA
• 1. Which nucleotide component is represented by a pentagon in diagrams? Pentose sugar  
• Which nitrogenous base is found in RNA, but not DNA? Uracil (U)
• 1. Explain the concept of antiparallel strands in DNA. DNA is made up of two polynucleotide strands, which run in opposite directions to each other. The left strand runs from the 5' end to 3' end, while the right strand runs from 3' end to 5' end.
• 1. Describe the process of forming the sugar–phosphate "backbone" in DNA and RNA. Sugar–phosphate backbone is formed from condensation reaction between the phosphate on the fifth carbon of one nucleotide to the hydroxyl group on the third carbon on an adjacent nucleotide. This forms a covalent phosphodiester bond. A series of these form the sugar-phosphate backbone. 
• Explain the role of hydrogen bonding in the formation of DNA’s structure. DNA is formed of two strands running antiparallel in a double helix structure. The nitrogenous bases point inward in the double helix, and form hydrogen bonds with nitrogenous bases on the opposite strand, holding the double helix together.
• Elaborate on the implications of the double helical structure of DNA in the context of genetic information storage and retrieval. = The double helical structure of DNA allows for efficient storage and retrieval of genetic information. The sequence of base pairs provides a code that dictates the synthesis of proteins and the maintenance of cellular functions.
• Draw and label the structure of a DNA nucleotide, clearly indicating the positions of the phosphate, pentose sugar, and nitrogenous base.

  
• Illustrate the differences between DNA and RNA

  
• DNA vs RNA nucleotides

  
• DNA


  • Forms a double stranded helix
  • Has two sugar-phosphate backbones
  • Bases of the two strands hydrogen bond with each other to maintain the structure
• RNA


  • Has one sugar-phosphate backbone
  • Depending on the type, the molecule can twist and bind to itself
• Main types of RNA involved in protein synthesis

  • mRNA
  • rRNA
  • tRNA
• Messenger RNA (mRNA)


  Transcripts a copy of a gene encoding for a specific polypeptide
• Transfer RNA (tRNA)


  Carries amino acids to the ribosome synthesizing a polypeptide
• Ribosomal RNA (rRNA)


  A primary component of ribosomes and is the catalyst/organelle where proteins are synthesised
• The 5’ and 3’ directionality of DNA and RNA affect the way enzymes can bind to and function when bound to the nucleic acids.

  • DNA polymerase, the enzyme involved in DNA replication
  • RNA polymerase, the enzyme which is involved during transcription (copy of the DNA gene is made in the form of mRNA)
  • Ribosome during translation

  The enzymes of transcription, RNA polymerase, can only add nucleotides to the 3’ end of a growing polymer of RNA nucleotides. The 5’ phosphate end is added to the 3’ ribose end of the growing RNA strand.  In this way, transcription is 5’ to 3’.
• Eukaryotic DNA


  DNA associated with proteins called histones which forms chromatin
• Formation of nucleosome


  1. DNA coils around a core of histone proteins (an octamer)

  2. DNA takes two turns around the octamer

  3. Additional histone protein (H1) holds the DNA in place
• Chromatosome


  Structure formed when H1 histone joins nucleosomes together, looks like a 'string of beads'
• Chromatin structure


  • Helps the DNA in eukaryotes to super coil, creating a compact structure which saves space in the nucleus