1.5 Nucleic acid

• What are nuclei acid and their function?

  nuclei acids (DNA/RNA) are polymers of nucleotides that store and transfer genetic information

  • DNA deoxyribonucleic acid - stores genetic material info
  • RNA ribonucleic acid - involved in protein synthesis
• what are the three components of a nucleotide?

  1. pentose sugar ( deoxyribose in DNA, robise in RNA)
  2. phosphate group
  3. nitrogenous base ( AT, CG in DNA/AU, CG in RNA)

  
• DNA vs. RNA

  DNA/RNA

  • pentose sugar - dioxyribose/ ribose
  • strands - double stranded/single stranded
  • bases - AT, CG/ AU, CG
  • function - stores genetic info transfers genetic code for protein synthesis
• How are nucleotides joined together?

  condensation reactions from phosphodiester bonds, between the phosphate group of one nucleotide and the sugar of another, creating the sugar-phosphate backbone.
• what is the structure of DNA

  • double helix
  • complementary base pairing held by hydrogen bonds
  • sugar-phosphate backbone provides stability
• How do bases pair in DNA?

  complementary base pairing

  • Adenine (A) pairs with Thymine (T) (2 hydrogen bonds).
  • Cytosine (C) pairs with Guanine (G) (3 hydrogen bonds).
• what are the steps of DNA replication?

  Semi-consevative replication

  • DNA helicase breaks hydrogen bonds, unwinding the helix.
  • each strands acts as a template.
  • free nucleotides pair with exposed bases using complimentary base pairing.
  • DNA polymerase forms phosphodiester bonds between the nucleotides.
  • two identical DNA molecules are produced each with one original and one new strand.
• Evidence for semi-conservative replication

  Meselson and Stahl's experiment

  • used nitrogen isotopes to track DNA replication.
  • DNA settled an intermediate density, proving each new DNA molecule contained one old and one new strand
• RNA types and their function

  • mRNA - carries genetic code from DNA to ribosomes
  • tRNA - brings amino acids to ribosomes for protein synthesis.
  • rRNS - forms part of ribosomes and aids in translation
• what happens during transcription

  protein synthesis - step 1

  • DNA helicase unwinds DNA
  • RNA polymerase joins free RNA nucleotides to form mRNA.
  • mRNA leaves the nucleus through the nuclear pore.
• what happens during translation?

  Protein synthesis step 2

  • mRNA attaches to a ribosome
  • tRNA molecules bring amino acids to the ribosome
  • peptide bonds form between amino acids creating a polypeptide chain
• What are gene mutations?

  changes in DNA base sequence that can alter protein function. types include:

  • substitution - one base is swapped ( a base is replaced with another base)
  • insertion/deletion - causes frameshift, altering all codons after mutation ( a base is removed or added to the NA sequence).