Nucleic Acids

• Give some similarities and differences of a homologous pair of chromosomes.

  • They're the same size with the same genes but the version of the gene (allele) could be different.
• What is an intron?

  • Genes contain introns and multiple repeats which do not code for a protein.
• What is an exon?

  • Exons are the coding parts of a gene
• What does a gene do?

  • A gene codes for one polypeptide
• Do prokaryotes or eukaryotes have introns?

  • Only eukaryotes do
• What can genes be divided into?

  • Triplets
• How long are triplets?

  • 3 bases long
• What does every condon carry?

  • The specific 3 letter sequence for a single amino acid.
• What is a genome?

  • The full set of genes possessed by an organism
• What is a proteome?

  • The entire set of proteins expressed by the genes in a genome.
• A protein has 4 amino acids, so the minimum number of bases that could code for this protein is 135 - why may the true number of bases be more than this?

  • Due to the presence of introns and multiple repeats that do not code for anything.
• Give three features of genetic code

  • Degenerate, non-overlapping and universal.
• A feature of genetic coding is that it's degenerate - what does this mean?

  Most of the amino acids have more than 1 triplet coding for them.
• A feature of genetic coding is that it's non-overlapping - what does this mean?

  • Each base is part of only 1 triplet so it is read only once in one direction.
• A feature of genetic coding is that it's universal - what does this mean?

  • The same triplets are present for the same amino acids in all living organisms.
• What's the relationship between DNA, RNA and proteins?

  • DNA carries genetic code but can't leave the nucleus and proteins are made at ribosomes on the rough ER.
  • So mRNA copies the DNA code and sends it to the ribosomes.
  • tRNA is found in the cytoplasm and delivers amino acids to the ribosome.
• Describe the structure of tRNA.

  • Clover leaf shaped.
  • Some areas of base pairing so some H bonds.
  • Anticodons match mRNA codons.
  • Amino acids attachment site carries one specific amino acid.
  • It's about 75 nucleotides long.
• Describe the structure of mRNA.

  • RNA nucleotides.
  • Ribose pentose sugar.
  • Bases of adenine, cytosine, guanine and uracil.
  • A complementary copy of a gene.
  • no. of nucleotides depends on the length of the gene.
  • Phosphodiester bonds form a sugar phosphate backbone.
  • The molecule is linear.
  • It's a single helix.
  • No base pairs so no H bonds.
• Describe the shape of DNA

  • It's linear and double helix
• Is DNA a strong molecule? Why?

  • Yes, it has many H bonds to provide strength.
• Why is mRNA weaker than tRNA?

  • mRNA has no H bonds compared to tRNA which has some to provide strength.
• Which has an amino acid binding site; DNA, mRNA or tRNA?

  • tRN