3: nucleic acid

• Nucleotide is made out of?

  1. Pentose sugar
  2. Phosphate group
  3. Nitrogenous base
• DNA nucleotide

  1. deoxyribose (pentose sugar)
  2. phosphate group
  3. nitrogenous base
• RNA nucleotide

  1. ribose (pentose sugar)
  2. phosphate group
  3. nitrogenous base
• DNA

  deoxyribonucleic acid (DNA).

  is used to store genetic information -- also contains the instructions an organism requires to grow
• RNA

  ribonucleic acid

  used to make proteins from the instructions in DNA
• nucleotides join together by a condensation reaction to form a polynucleotide with phosphodiester bond.

  in the poly nucleotide the chains of sugars and phosphates is known as the sugar-phosphate backbone
• 2 DNA polynucleotide strands can be joined by hydrogen bonding between bases to form a double helix.

  antiparallel polynucleotide strands twist and form the DNA double-helix
• complementary base pairing 


  each base can only join with one particular partner

  eg.. A-T(3 H bonds) and C-G(2H bonds)
• DNA self-replication

  1. DNA helicase breaks the hydrogen bonds and the 2 polynucleotide strands unzip
  2. Both original strands act as a template for a new strand to be created. Then free floating DNA nucleotides can join to the exposed bases by complementary base pairing
  3. The newly added nucleotides are joined together DNA polymerase making a new strand based off of the original one. strands then twist to form a double helix
  4. semi-conservative replication
• random spontaneous mutation can happen in self- replication this is any change to the DNA base sequence
• what is a gene?

  a sequence of DNA nucleotides that code for a polypeptide.

  Also are the instructions for making proteins
• How is DNA copied into RNA for protein synthesis?

  1. DNA is too large to leave the nucleus, therefore a section of it is copied into mRNA (this is called transcription)
  2. the mRNA leaves the nucleus and joins with a ribosome where it can be used to synthesise a protein (this is called translation)
• mRNA?

  -- made in the nucleus

  -- three adjacent bases are called a codon

  -- carries the genetic code from DNA to cytoplasm where it can make protein during translation
• tRNA?


  -- found in cytoplasm

  -- has amino acid binding site at one end and and a sequence of three bases at the other end called anticodon

  -- carries amino acids for making of protein to the ribosome during translation
• rRNA?

  -- forms 2 subunits in a ribosome

  -- the ribosome moves up mRNA strand during protein synthesis the rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids
• TRANSCRIPTION pt 1

  1. starts when RNA polymerase attaches to DNA at the beginning of gene
  2. H bonds break separating the 2 DNA strands
  3. one of the strands is used as a template to make mRNA copy
  4. RNA polymerase lines up free RNA nucleotides. alongside OG strand... complementary base pairing
  5. RNA pair up with specific bases on DNA strand they form mRNA molecule
• transcription pt 2

  6. RNA polymerase moves along the DNA separating strands and

  assembling mRNA strand

  7. hydrogen bonds between the uncoiled strands reform nonce

  the RNA polymerase has passed by and the strands can coil back

  into a double helix

  8. when RNA reaches a stop codon it stops making mRNA and

  detaches from DNA

  9. mRNA moves out of the nucleus via nuclear pore and attaches

  to a ribosome in the cytoplasm
• TRANSLATION

  1. mRNA attaches itself to a ribosome and the tRNA molecules carry amino acids to the ribosome
  2. a tRNA with an anticodon attaches itself to the mRNA by complementary base pairing
  3. second tRNA molecule does the same thing as before
  4. rRNA in ribosome catalyses the formation of a peptide bond. this joins the amino acids. first tRNA molecules move away leaving amino acid behind
  5. 3rd tRNA binds to the next codon and second tRNA moves away
  6. process repeated until stop codon
  7. polypeptide chain moves away
• what are the 2 stages of protein synthesis called?

  Transcription and Translation
• what is the base in ATP and ADP?

  adenine
• How are nucleotides joined together in DNA? 3marks

  -- nucleotides join via condensation reactions

  -- forming a phosphodiester bond

  -- this is known as a sugar phosphate backbone
• Chemical released when bond is formed between 2 nucleotides?

  Water