Mutations and Protein Function

The video tutorial explains nonsense mutation, a type of point mutation where a single nucleotide change in DNA or mRNA results in a premature stop codon, leading to truncated proteins. This mutation can cause faulty proteins with altered or no function, potentially leading to cellular issues. The tutorial provides an example using the CAG codon, which normally codes for glutamine, but a mutation changes it to a stop codon, halting protein synthesis. The video also discusses the potential consequences of truncated proteins, including improper function or degradation, and contrasts nonsense mutation with missense mutation.

What is a nonsense mutation?

• A mutation that results in the addition of extra nucleotides.

• A mutation that has no effect on protein synthesis.

• A mutation that changes a single nucleotide, leading to a stop codon.

• A mutation that causes a frameshift in the DNA sequence.

What does the CAG codon code for?

• Serine

• Valine

• Glutamine

• Lysine

What happens when a CAG codon is mutated to a TAG codon?

• It has no effect on the protein.

• It becomes a stop codon, halting protein synthesis.

• It results in a frameshift mutation.

• It codes for a different amino acid.

What is the role of UAG in mRNA?

• It codes for an amino acid.

• It serves as a stop codon.

• It is involved in splicing.

• It acts as a start codon.

How does a truncated protein affect cellular function?

• It always functions better than the original protein.

• It enhances the function of other proteins.

• It may have a different or no function, potentially causing cellular issues.

• It has no impact on cellular function.

What happens to truncated proteins that do not function properly?

• They are degraded by cellular mechanisms.

• They are stored for later use.

• They are repaired by the cell.

• They are converted back to their original form.

What is the potential outcome of a truncated protein combining with another truncated protein?

• It is immediately degraded.

• It forms a functional protein.

• It forms a new type of protein with unknown functions.

• It repairs the original protein.

What is the main difference between nonsense and missense mutations?

• Nonsense mutations occur in RNA, while missense mutations occur in DNA.

• Nonsense mutations have no effect, while missense mutations cause frameshifts.

• Nonsense mutations add extra nucleotides, while missense mutations delete nucleotides.

• Nonsense mutations result in a stop codon, while missense mutations change an amino acid.

In a missense mutation, what happens to the protein?

• It is truncated.

• It is not produced at all.

• It has a different amino acid sequence.

• It is identical to the original protein.

Why is a nonsense mutation considered 'nonsense'?

• Because it results in a non-functional protein.

• Because it adds extra nucleotides.

• Because it has no effect on the protein.

• Because it causes a frameshift.