Mutations

• What is the starting molecule for translation?

  mRNA
• What does mRNA associate with during translation?

  Ribosome
• What is the start codon in translation?

  AUG
• What does tRNA bring to the ribosome?

  Specific amino acid
• How does the anticodon on tRNA relate to mRNA?

  It is complementary to the codon
• What happens as the ribosome moves along mRNA?

  It moves to the next codon
• What type of bond forms between amino acids during translation?

  Peptide bonds
• What is a gene mutation?

  A change in the DNA sequence
• What is a substitution mutation?

  Replacing one nucleotide with another
• What is a silent mutation?

  Same amino acid coded as original
• What is a non-sense mutation?

  Leads to a premature stop codon
• What is the effect of a non-sense mutation?

  Premature end to polypeptide synthesis
• What are the stop codons?

  UAA, UAG, UGA
• What disease is associated with non-sense mutations?

  Thalassemia
• What is a mis-sense mutation?

  Change in base leads to different amino acid
• How does a mis-sense mutation affect a polypeptide?

  It changes one amino acid in the sequence
• What mutation causes sickle cell disease?

  A mis-sense mutation in the haemoglobin gene
• What amino acid is replaced in sickle cell disease?

  Glutamic acid is replaced by Valine
• What is the result of the amino acid change in sickle cell disease?

  Distorted shape of red blood cells
• What happens during deletion or addition of bases?

  It leads to a frame shift in codons
• What disease is caused by deletion or addition of bases?

  Tay-Sachs disease
• What is Tay-Sachs disease?

  An autosomal recessive disorder
• What enzyme is insufficient in Tay-Sachs disease?

  Hexosaminidase
• What accumulates in the brain due to Tay-Sachs disease?

  Lipids
• What are chromosome mutations?

  Changes in the structure or number of chromosomes
• What is polyploidy?

  Change in the whole set of chromosomes
• Where does polyploidy mostly occur?

  In plants
• What is non-disjunction?

  Failure of homologous chromosomes to separate
• What condition is caused by non-disjunction of chromosome 21?

  Down's syndrome
• What can cause mutations during DNA replication?

  Errors by DNA polymerase
• What are mutagenic agents?

  Agents that increase mutation frequency
• What are examples of mutagenic agents?

  High energy radiation and chemicals
• What is the role of hexosaminidase?

  To break down lipids in lysosomes
• What happens if the active site of an enzyme is changed?

  Inactive enzyme if substrate cannot bind
• What are the effects of different mutations in DNA?

  • Silent mutation: No effect on protein
  • Non-sense mutation: Premature stop codon
  • Mis-sense mutation: Different amino acid coded
  • Deletion/addition: Frame shift in codons
• What are the causes of mutations?

  • Mistakes during DNA replication
  • Mutagenic agents (radiation, chemicals)
• What are the types of chromosome mutations?

  • Polyploidy: Change in whole set of chromosomes
  • Non-disjunction: Failure of homologous chromosomes to separate
• What is the significance of mutations in genetics?

  • Can lead to genetic diversity
  • May cause genetic disorders
  • Important in evolution