lesson 2

• Nucleic Acids


  Long chains of nucleotides (monomers)
• Nucleotide


  Composed of phosphate, sugar, and a nitrogen base
• Types of nucleic acids

  • DNA
  • RNA
• Functions of nucleic acids


  • Store/transmit genetic information
  • Instructions for making proteins
• DNA

  Deoxyribonucleic Acid
• DNA


  • Shaped as a double helix
  • Designed by Watson and Crick
  • Contains genetic information stored in chromosomes in the nucleus of cells
• DNA sugar

  Deoxyribose
• DNA nitrogen bases


  • Adenine(A)
  • Guanine(G)
  • Cytosine(C)
  • Thymine(T)
• Purines


  Double-ringed nitrogen base structures
• Pyrimidines


  Single-ringed nitrogen base structures
• Adenine(A) and Guanine(G) are purines, Cytosine(C) and Thymine(T) are pyrimidines
• Chargaff's Rule


  Number of A = number of T, and number of C = number of G
• Complementary base pairing


  A pairs with T, C pairs with G
• Hydrogen bonds

  Weak bonds that hold nitrogen bases together
• DNA orientation

  • Runs antiparallel (opposite directions)
  • 5' phosphate end
  • 3' -OH end
• The nucleotide sequence is unique for each species and individual
• RNA

  Ribonucleic Acid, single stranded
• RNA sugar

  Ribose
• RNA nitrogen bases

  • Cytosine(C)
  • Guanine(G)
  • Adenine(A)
  • Uracil(U)
• Complementary RNA base pairing

  A and U pair, C and G pair
• Types of RNA

  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
• DNA and RNA differ in: strandedness, sugar, nitrogen bases, replication ability, and number of types
• In eukaryotic cells, DNA is stored in the nucleus. DNA is stored in a compact ball called chromatin, and is wrapped around proteins called histones to form nucleosomes.
• Hydrogen bonds between base pairs are broken by the enzyme helicase and DNA molecule unzips
• DNA Replication

  DNA in the parent cell must be replicated before the cell divides - this process occurs during interphase in the cell cycle.
• Nucleotides are linked into 2 new strands of DNA by the enzyme polymerase - proofreads for copying errors.
• When eukaryotic cell divides, the process is called mitosis
• semi-conservative replication: each new strand is a combination of the original strand and the newly synthesized strand
• Replication fork is the open DNA section where the DNA strands are being replicated.
• Formation of 5'-3' ester bonds of the leading strand, the lagging strand growns in the 3'-5' direction, is synthesize in short sections called Okazaki fragments
• the genetic code is found in the sequence of nucleotides in mRNA that is translated from the DNA
• A codon is a triplet of bases along the mRNA that codes for a particular amino acid
• triplet code for a specific amino acid ex: CGA - CAA - CCA - GCT - GGG - GAG - CCA