DNA

• DNA structure and its relation to its functions


  • Sugar-phosphate (backbone) and double stranded to provide strength and stability (protects H bonds)
  • Double stranded so replication can occur semi-conservatively (strands can act as templates)
  • Helix/coiled so that DA is compact
  • Weak hydrogen bonding for replication (unzipping DNA strands easily)
  • Large molecule so it can store lots of information
  • Base sequence allows information to be stored- base sequence codes for amino acids
• DNA


  • Long/large molecule so can store lots of information
  • Helix/coiled so compact
• Base sequence


  Allows information to be stored/codes for amino acids/protein
• DNA structure


  • Double stranded so replication can occur semi-conservatively
  • Strands can act as templates
  • Complementary base pairing (A-T, G-C) so accurate replication/identical copies can be made
• Hydrogen bonds


  • For replication/unzipping/strand separation
  • Many hydrogen bonds so stable/strong
• Variation is genetic 


  -offspring of the same family will be more similar genetically, this is due to them having the same parents

  -it is expected to see more differences in randomly chosen cheetahs
• why is there differences in the percentage of the same base in the two species

  different genes have different DNA base sequence
• genetic code is degenerate

  • 1 amino acid is coded for by more than 1 triplet
• Codon


  sequence of 3 bases on an mRNA strand that code for an amino acid
• What is the role of RNA polymerase during transcription?

  joins nucleotides together to form an mRNA strand via phosphodiester bonds
• Describe how mRNA is produced in the nucleus of a cell

  -DNA helicase breaks hydrogen bonds and unzips DNA strands

  -only one of the DNA strands acts as a template strand

  -RNA nucleotides attach to exposed bases, the attraction occurs according to base pair ruling

  -DNA polymerase joins adjacent nucleotides and this continues until a stop codon is reaches

  -pre-mRNA then detaches from the template strand

  -splicing occurs to the pre-mRNA to remove introns, thus forming mRNA
• what is genetic diversity?

  Difference in base equine of DNA
• Genetic code being universal

  -in all organisms, the same triplet codes for the same amino acid
• how does the process of translation lead to the production of a polypeptide?

  -mRNA attaches to ribosome

  -codon on mRNA binds to anti-codon on tRNA

  -each tRNA brings a specific amino acid

  -the sequence of codon on the mRNA determines the order of amino acids

  -Amino acids are joined together by the formation of peptide bonds
• How do two amino acids differ from one another?

  different variable R groups
• What is a gene?

  length of DNA
• What is ribosome made out of?

  One protein and one RNA
• ribosomes assembly polypeptides using mRNA code
• DNA in chloroplasts Vs DNA in nucleus

  DNA in chloroplasts is shorter

  there are fewer genes in the DNA in chloroplasts

  DNA in chloroplasts do not contain histone, DNA in nucleus is associated with histones
• Condesnation reaction between phosphate and deoxyribose forms a phosphodiester bond.

  This is catalysed by DNA polymerase
• Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.

  Nucleotide structure is identical and the nucleotides are joined by phosphodiester bonds

  DNA in mitochondria has a similar structure to DNA in prokaryotes

  Eukaryotic DNA is longer

  Eukaryotic DNA contains introns, prokaryotic DNA doesn’t

  Eukaryotic DNA is linear, prokaryotic DNA is circular

  Eukaryotic DNA is associated with hi stones , prokaryotic DNA is not