DNA & RNA

• What does DNA stand for ?

  deoxyribonucleic acid
• What does RNA stand for?


  Ribonucleic acid
• DNA & RNA are both types of....

  nucleic acid ( polymers of nucleotides)
• a nucleotide is a type of biological molecule what's it made from ?

  1. a pentose sugar ( sugar with 5 carbon atoms)
  2. a nitrogen-containing organic base (organic meaning containing carbon)
  3. a phosphate group

  
• Similarity's between the functions of DNA & RNA:

  • DNA and RNA are both needed to build proteins, which are essential for the proper functioning of cells
  • DNA and RNA are both important information-carrying molecules,
• Function of DNA:

  1. The function of DNA is to hold or store genetic information
  2. DNA is the molecule that contains the instructions for the growth and development of all organisms
• Function of RNA:

  1. The function of RNA is to transfer the genetic code found in DNA out of the nucleus and carry it to the ribosomes in the cytoplasm

  • Ribosomes are where proteins are produced - they ‘read’ the RNA to make polypeptides (proteins) in a process known as translation - ribosomes themselves are made of RNA and proteins
• DNA structure:

  1. pentose sugar in DNA nucleotide = deoxyribose
  2. Each DNA nucleotide has the same sugar and phosphate group but the base on each nucleotide can vary
  3. 4 possible bases = adenine (A), thymine (T), cytosine (C), guanine(G)

  
• Structure of RNA:

  1. pentose sugar in RNA = ribose sugar
  2. Like DNA , an RNA nucleotide also has a phosphate group and on of 4 different bases
  3. In RNA, uracil (U) replaces thymine as a base

  
• RNA possible bases =

  1. Adenine
  2. Cytosine
  3. Guanine
  4. Uracil
• DNA possible bases =

  1. Adenine
  2. Cytosine
  3. Guanine
  4. Thymine
• What is a polynucleotide ?

  • a polymer of nucleotides - both DNA and RNA nucleotides form polynucleotides
• How do the nucleotides join up to become polynucleotides?

  1. via a condensation reaction between the phosphate group of one nucleotide and the pentose sugar of another
  2. this forms a phosphodiester bond (consisting of the phosphate group and two ester bonds) - catalysed by DNA polymerase
  3. The chain of sugars and phosphates is known as the sugar- phosphate backbone

  
• What's the name of the bond which forms between the phosphate group and pentose sugar of 2 nucleotides ?

  Phosphodiester bond - consisting of the phosphate group and 2 ester bonds

  
• How do 2 DNA polynucleotide join together ?

  by hydrogen bonding between the bases

  
• What's each bases complimentary base pairing?

  1. Adenine & Thymine (A-T)
  2. Cytosine & Guanine (C-G)
  3. Therefore it means there are always equal amount of adenine and thymine in a DNA molecule and equal amounts of cytosine and guanine
• how many hydrogen bonds are between each complimentary base pairing ?

  • 2 hydrogen bonds form between A & T
  • 3 hydrogen bonds form between C & G - this means the more C-G pairings the more stable the DNA
• Explain the DNA double helix :

  • DNA molecules exist as a double helix
  • consist of 2 antiparallel polynucleotide strands held together by hydrogen bonds between complimentary base pairs
• Compare DNA & RNA =

  1. DNA is double stranded (2 polynucleotide strands), RNA is single stranded (1 polynucleotide strand)
  2. DNA contains deoxyribose, RNA contains ribose
  3. DNA contains Thymine which in RNA is replaced by Uracil
  4. RNA is a smaller molecule than DNA (shorter)
  5. They are both polymers
• What was determined by Watson and Crick ? (JUSTICE FOR ROSALIND FRANKLIN)

  • 1953 - experiments had shown that DNA was the carrier of the genetic codes (which had been doubted previously due to its simple chemical composition). This was also the year in which the double- helix structure, which helps DNA to carry out its function was determined by Watson and Crick