Nucleic acids

• Some viruses use RNA as their genetic material but viruses are not considered to be living.
• DNA


  Deoxyribonucleic acid, the genetic material for all living organisms
• DNA is found in chromosomes and contains the genetic information for the growth and development of individual cells and organisms.
• The use of the genetic code across all forms of life is evidence of universal common ancestry of life (A1.2.10).
• The sequences of DNA in cells can be analyzed and compared to determine evolutionary relationships between organisms (A3.2.6).
• The more similar the sequence, the more closely related the organisms (A3.2.5).
• Viruses


  Contain genetic material (DNA or RNA) which is surrounded by a protein coat, but most scientists do not consider viruses as living
• Characteristics of life that viruses do not possess

  • Cells which carry out metabolism and homeostasis
  • Ability to respond to stimuli
  • Ability to grow
  • Ability to reproduce themselves (they are replicated by host cells)
• Coronavirus 2019
• In diagrams of nucleotides use circles, pentagons and rectangles to represent relative positions of phosphates, pentose sugars and bases.
• Sugar–phosphate bonding makes a continuous chain of covalently bonded atoms in each strand of DNA or RNA nucleotides, which forms a strong "backbone" in the molecule.
• Components of RNA and DNA nucleotides

  • Phosphate
  • Sugar
  • Nitrogen base
• The sugar for RNA is Ribose, the sugar for DNA is Deoxyribose.
• Nitrogen bases in RNA

  • Uracil
  • Adenine
  • Cytosine
  • Guanine
• Nitrogen bases in DNA

  • Thymine
  • Adenine
  • Cytosine
  • Guanine
• DNA is located in the nucleus
• DNA


  Deoxyribonucleic acid
• Double helix


  The shape of DNA
• DNA


  The blueprint of life
• Where DNA has Thymine, RNA has Uracil
• Polynucleotides


  Both DNA and RNA are formed through a series of condensation (2-1) reactions
• Covalent bond


  Forms between the phosphate of one nucleotide, and the sugar of the second nucleotide
• Students should know the names of the nitrogenous bases.
• Students should be able to draw and recognize diagrams of the structure of single nucleotides and RNA polymers.
• Drawing RNA


  1. Draw at least four nucleotides in a vertical column

  2. Add a covalent bond between the ribose sugar of one nucleotide and the phosphate of the nucleotide below it

  3. Add the names of the RNA nitrogen bases to the diagram
• RNA nitrogen bases


  • Uracil
  • Adenine
  • Cytosine
  • Guanine
• Labelling RNA


  • Uracil
  • Adenine
  • Cytosine
  • Guanine
  • Nucleotide
  • Ribose
  • Nitrogen Base
  • Phosphate
  • Covalent Bond
• The tRNA molecule in the diagram includes the nitrogen bases uracil, adenine, cytosine, and guanine.
• In diagrams of DNA structure, students should draw the two strands antiparallel, but are not required to draw the helical shape. Students should show adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). Students are not required to memorize the relative lengths of the purine and pyrimidine bases, or the numbers of hydrogen bonds.
• Hydrogen bonds


  Weak chemical attractions between two polar molecules that hold the DNA double helix together
• Complementary base pairing


  Bases pair up with each other in a consistent way, with adenine pairing with thymine (2 hydrogen bonds) and guanine pairing with cytosine (3 hydrogen bonds)
• Double Helix


  DNA has a double helix shape, as two strands of polynucleotides form intertwined helices
• Complementary base pairs


  Nucleotides can only form hydrogen bonds with specific nucleotides. In DNA, adenine is the complementary base of thymine, and guanine is the complementary base of cytosine.
• Antiparallel


  The DNA strands run in opposite directions
• Drawing DNA


  1. Draw and label a single DNA nucleotide

  2. Join the two nucleotides together by a covalent bond, between the phosphate and deoxyribose

  3. Draw a nucleotide on the opposite side, ensuring it is antiparallel

  4. Add a second nucleotide to the right-hand side and connect with a covalent bond

  5. Add hydrogen bonds between the nitrogen bases and label them

  6. Add the names of the nitrogen bases using complementary base pairing

  7. Add labels for phosphate, hydrogen bonds, deoxyribose, covalent bond, nucleotide, and nitrogen base
• Students should be able to sketch the difference between ribose and deoxyribose. Students should be familiar with examples of nucleic acids.
• Distinguish between the structure of RNA and DNA


  • Number of Strands: 1 (RNA), 2 (DNA)
  • Sugar: Ribose (RNA), Deoxyribose (DNA)
  • Nitrogen Bases: Uracil, Adenine, Cytosine, Guanine (RNA), Thymine, Adenine, Cytosine, Guanine (DNA)
  • Pairing rules: Complementary base pairing
• Other differences between RNA and DNA

  • Function: DNA passes heredity information, RNA codes for making RNA and proteins
  • Location in Eukaryotes: DNA in nucleus, small amount in chloroplast and mitochondria, RNA made in nucleus and transported to cytoplasm
  • Location in Prokaryotes: DNA in nucleoid, RNA in cytoplasm
• Students should understand that complementarity is based on hydrogen bonding.
• Complementary base pairing for Replication

  1. Guanine only allows cytosine to bond to it, forming three hydrogen bonds

  2. Thymine only allows adenine to bond to it, forming two hydrogen bonds