AP Biology : Understand mutations that can arise

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understand Mutations That Can Arise

What is the result of a silent mutation?

Possible Answers:

There is no change to the peptide product

Early termination of translation

Inclusion of a different amino acid

A shift in the reading frame that results in a nearly completely different protein

Correct answer:

There is no change to the peptide product

Explanation:

As the name suggests, silent mutations are point mutations that actually have no visible effect on the protein. This is due to the degeneracy of the genetic code. Several codons actually insert the same amino acid. It is possible to mutate a codon so that it actually inserts the same amino acid. For example, if the codon UCU were mutated to UCG, it will still recruit the amino acid serine.

The other answers describe other types of mutations. Missense mutations are point mutations that result in the swapping of one amino acid for another. Nonsense mutations cause early termination. Frameshift mutations shift the reading frame of the codon sequence, severely altering the protein composition.

Example Question #1 : Understand Mutations That Can Arise

Which of the following describes abortive initiation?

Possible Answers:

Short cycles of RNA synthesis

Arrest of transcription due to error

The inability of the initiation complex to form

RNA polymerase cannot bind to the promoter sequence

Correct answer:

Short cycles of RNA synthesis

Explanation:

Abortive initiation is the process by which RNA polymerase starts short cycles of RNA synthesis. During abortive initiation, RNA polymerase releases short RNA strands before the initiation complex leaves the promoter sequence. Abortive initiation is a common process in both eukaryotes and prokaryotes.

Example Question #2 : Central Dogma

If a DNA sequence is mutated from AGCTAA to AGCCTAA, what kind of mutation has occurred?

Possible Answers:

Substitution

Point mutation

Insertion

Deletion

Correct answer:

Insertion

Explanation:

An insertion mutation is a mutation due to an additional nucleotide base pair being added to a DNA sequence. In this case, a cytosine nucleotide has been inserted.

Example Question #2 : Understand Mutations That Can Arise

If a DNA sequence is mutated from AGCTAA to AGCAAA, what type of mutation has occurred?

Possible Answers:

Substitution

Deletion

Insertion

Frameshift

Correct answer:

Substitution

Explanation:

A substitution mutation occurs when a base pair is exchanged for a different base pair. In this case, a thymine nucleotide has been substituted for an adenine nucleotide.

Example Question #4 : Central Dogma

If a DNA sequence experiences an insertion mutation, what consequence may this have on the DNA sequence?

Possible Answers:

Prevent RNA polymerase from binding

Cause a point mutation

Cause a frameshift mutation

Cause a deletion

Correct answer:

Cause a frameshift mutation

Explanation:

An insertion mutation that occurs where an amount of nucleotides that is not a multiple of three is added to a DNA sequence will shift the reading frame.

Example Question #4 : Central Dogma

If a DNA sequence is mutated from TCCGGA to TCGGA, what type of mutation has occurred?

Possible Answers:

Point

Substitution

Deletion

Insertion

Correct answer:

Deletion

Explanation:

A deletion mutation occurs when a base pair is removed from the DNA sequence. In this case, a cytosine nucleotide has been deleted.

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