Lecture 07

• What is the relationship between DNA sequence and protein?

  It determines the amino acid sequence
• What is a reading frame?

  The way nucleotides are grouped into codons
• What are codons associated with?

  Amino acids and stop codons

  
• How universal is the genetic code?

  It is nearly universal
• What role do mutations play in the genetic code?

  They help verify the genetic code
• What are the four bases of DNA?

  Adenine, Guanine, Cytosine, Thymine

  
• How many common amino acids are encoded by DNA?

  20 common amino acids
• How many nucleotides are needed to encode one amino acid?

  1 nucleotide for 4 amino acids
• How many different amino acids can be encoded with 2 nucleotides?

  16 amino acids
• How many different triplet combinations can 3 nucleotides create?

  64 different triplet combinations
• What is a codon?

  A three-letter word in mRNA

  
• What does a codon consist of?

  Three consecutive bases specifying an amino acid

  
• What type of mutation results in a different amino acid?

  Missense mutation
• What happens during a nonsense mutation?

  Protein synthesis stops prematurely
• What is a frameshift mutation?

  Change in whole triplet codon due to insertion or deletion

  
• What are point mutations?

  Changes in a single nucleotide base
• What are the types of point mutations?

  Silent, missense, and nonsense mutations
• What are the two types of frameshift mutations?

  Insertion and deletion

  
• What is a silent mutation?

  It results in the same amino acid
• What happens in a frameshift mutation?

  Amino acids change from the mutation point
• What are the consequences of a nonsense mutation?

  Protein synthesis stops, producing truncated protein
• What is sickle cell anemia?

  A genetic disease with severe symptoms
• What causes sickle cell anemia?

  A mutated version of the haemoglobin gene

  
• How many copies of the sickle cell gene are needed?

  Two copies are needed
• What are the DNA level effects of sickle cell anemia?

  Mutation changes the haemoglobin gene

  
• What are the protein level effects of sickle cell anemia?

  Changes the shape of the haemoglobin molecule
• What are the cellular level effects of sickle cell anemia?

  Red blood cells become sickle-shaped

  
• What are the whole organism effects of sickle cell anemia?

  Symptoms like pain and fatigue under stress
• What is a positive effect of the sickle cell allele?

  Resistance to malaria in carriers
• How do sickle-shaped blood cells affect malaria parasites?

  Parasites are killed inside sickle-shaped cells
• What is the total number of different possible codons?

  64 different possible codons
• How many codons specify amino acids?

  61 codons specify amino acids

  
• How many codons signal stop?

  3 codons signal stop
• Which statement about the genetic code is false?

  The genetic code is overlapping
• What is the effect of a deletion of a single nucleotide?

  It could lead to a missense mutation
• What are the types of mutations and their effects?

  • Missense: different amino acid, different protein
  • Nonsense: stops protein synthesis, truncated protein
  • Frameshift (deletion): changes whole triplet codon
  • Frameshift (insertion): alters reading frame
• What are the consequences of mutations on protein products?

  • Silent: same amino acid
  • Missense: different amino acid
  • Frameshift: changes all subsequent amino acids
  • Nonsense: stops synthesis, truncated protein
• What are the levels of effects of sickle cell anemia?

  1. DNA level: mutation in haemoglobin gene
  2. Protein level: altered haemoglobin shape
  3. Cellular level: sickle-shaped red blood cells
  4. Whole organism: symptoms under stress
  5. Positive: resistance to malaria