AP Biology : Understand mutations that can arise
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Example Question #1 : Central Dogma
What is the result of a silent mutation?
A shift in the reading frame that results in a nearly completely different protein
Inclusion of a different amino acid
There is no change to the peptide product
Early termination of translation
There is no change to the peptide product
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 : Central Dogma
Which of the following describes abortive initiation?
Arrest of transcription due to error
Short cycles of RNA synthesis
RNA polymerase cannot bind to the promoter sequence
The inability of the initiation complex to form
Short cycles of RNA synthesis
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 #1 : Central Dogma
If a DNA sequence is mutated from AGCTAA to AGCCTAA, what kind of mutation has occurred?
Point mutation
Deletion
Insertion
Substitution
Insertion
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 #1 : Central Dogma
If a DNA sequence is mutated from AGCTAA to AGCAAA, what type of mutation has occurred?
Frameshift
Insertion
Substitution
Deletion
Substitution
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 #2 : Central Dogma
If a DNA sequence experiences an insertion mutation, what consequence may this have on the DNA sequence?
Cause a frameshift mutation
Prevent RNA polymerase from binding
Cause a deletion
Cause a point mutation
Cause a frameshift mutation
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 #2 : Central Dogma
If a DNA sequence is mutated from TCCGGA to TCGGA, what type of mutation has occurred?
Deletion
Point
Substitution
Insertion
Deletion
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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