Mutations and Codon Structure

The video explains how Francis Crick and colleagues determined that a codon in the genetic code consists of three nucleotides, forming a triplet. Through experiments with acridine-induced mutations, they discovered that adding or deleting nucleotides disrupts the reading frame, leading to nonfunctional proteins. However, combining mutations can restore gene function, supporting the triplet nature of codons.

What did Francis Crick and his colleagues determine about the structure of a codon?

• A codon consists of three nucleotides.

• A codon consists of four nucleotides.

• A codon consists of two nucleotides.

• A codon consists of five nucleotides.

What is the effect of a deletion mutation on the protein level?

• It slightly alters the protein function.

• It results in complete gibberish and destroys the protein function.

• It has no effect on the protein function.

• It enhances the protein function.

What is the role of acridine in the study of mutations?

• It enhances the DNA sequence.

• It introduces mutations by adding or deleting nucleotides.

• It repairs the DNA sequence.

• It stabilizes the DNA sequence.

How does an addition mutation affect the reading frame?

• It does not affect the reading frame.

• It causes a re-registration of the reading frame.

• It enhances the reading frame.

• It shortens the reading frame.

What is the result of a single nucleotide addition in a gene sequence?

• It has no effect on the reading frame.

• It causes a re-registration of the reading frame.

• It enhances protein function.

• It shortens the reading frame.

What happens when an addition mutant and a deletion mutant are crossed?

• They form a non-functional protein.

• They do not interact.

• They form a triple mutant.

• They form a double mutant with restored gene function.

What is the effect of a short sequence of gibberish in a double mutant?

• It enhances the gene function.

• It slightly alters the gene function but does not destroy it.

• It has no effect on the gene function.

• It completely destroys the gene function.

What is the significance of combining three additions or deletions in a gene?

• It destroys the gene function.

• It has no effect on the gene function.

• It restores the reading frame and gene function.

• It creates a new gene function.

How did Crick and his colleagues confirm the triplet nature of codons?

• By observing single mutations.

• By combining two mutations.

• By combining three additions or deletions.

• By studying non-mutated genes.

What hypothesis did Crick and his co-workers support through their study?

• The hypothesis of a four-base codon.

• The hypothesis of a five-base codon.

• The hypothesis of a two-base codon.

• The hypothesis of a three-base codon.