8.1.1 Gene Mutations

• What are the three types of point mutations?

  Substitutions, insertions, deletions
• Silent mutations always change the protein sequence.

  False
• Match the type of mutation with its definition:

  Point mutations ↔️ Single base substitutions, insertions, or deletions

  Frameshift mutations ↔️ Insertions or deletions not a multiple of 3 base pairs
• In a substitution mutation, one nucleotide is replaced by a different nucleotide.
• If a missense mutation affects the active site of an enzyme, it can impair its function.
• Silent mutations can subtly influence protein folding, mRNA stability, and translation rate.
• What are point mutations defined as?

  Single base changes
• What is an example of a substitution in a DNA sequence?

  A to T
• What is the primary effect of missense mutations on protein structure?

  Altered protein folding
• Nonsense mutations change a codon coding for an amino acid into a stop codon.
• Which diseases are associated with nonsense mutations?

  Cystic fibrosis or Duchenne muscular dystrophy
• Silent mutations always affect protein folding and function.

  False
• Frameshift mutations always lead to a truncated protein.

  False
• What environmental factors can cause gene mutations?

  UV radiation or chemical mutagens
• What is the consequence of a nonsense mutation?

  Premature termination of translation
• Steps in DNA repair mechanisms

  1️⃣ Recognition of damaged DNA

  2️⃣ Excision of damaged DNA

  3️⃣ Replacement with correct nucleotides

  4️⃣ Ligation of DNA backbone
• What are point mutations caused by?

  Changes in a single nucleotide
• What is the result of a missense mutation?

  Substitution of one amino acid
• Why do silent mutations not affect protein function?

  Codon redundancy
• Gene mutations are changes in the DNA sequence of a gene.
• Gene mutations can lead to significant changes in the resulting protein.
• In a substitution, one nucleotide is replaced by a different nucleotide.
• Match the feature with its effect in a normal or mutant protein affected by missense mutations:

  Amino Acid Sequence ↔️ AGC or AGT

  Folding ↔️ Correct or misfolded

  Function ↔️ Normal or reduced activity
• A nonsense mutation always leads to a functional protein.

  False
• Silent mutations change a codon, but due to codon redundancy, the same amino acid is encoded.
• Frameshift mutations occur when insertions or deletions of nucleotides are not a multiple of 3.
• Errors during DNA replication can lead to mutations caused by mistakes made by DNA polymerase.
• Base Excision Repair (BER) uses glycosylase to remove a damaged base.
• Substitutions involve the replacement of one nucleotide with another.
• What factors can cause gene mutations?

  DNA damage, environmental agents
• Frameshift mutations alter the reading frame of the genetic code.


  True
• All point mutations change the amino acid sequence of a protein.

  False
• A nonsense mutation always produces a non-functional protein.


  True
• Frameshift mutations alter the reading frame of the genetic code.


  True
• Point mutations always change the amino acid sequence of a protein.

  False
• If a missense mutation occurs in the enzyme's active site, its catalytic activity may be impaired.

  True
• What is the result of a nonsense mutation on protein length?

  Truncated protein
• Match the feature with its effect in a normal or truncated protein affected by nonsense mutations:

  Amino Acid Sequence ↔️ AGCUAA or AG

  Folding ↔️ Correctly folded or unfolded

  Function ↔️ Normal or no activity
• What is an example of a silent mutation in DNA?

  AGC becomes AGT
• How does a frameshift mutation affect the codon reading frame?

  It shifts the frame