Pre AP Biology -GEN 3.4 Mutations- MCQ Exam Style Questions -New Syllabus

Pre AP Biology -GEN 3.4 Mutations- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -GEN 3.4 Mutations- MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.

Pre AP Biology – MCQ Exam Style Questions- All Topics

Question

Which one of these characteristics applies to prions?

a. They can be transmitted only from animals to humans.
b. The diseases they cause progress very rapidly.
c. They have an amino acid sequence different from the normal protein.
d. They reproduce by misfolding normal proteins.

▶️ Answer/Explanation

Detailed solution

The correct option is d.
Prions are infectious pathogens composed entirely of protein material.
They do not contain nucleic acids like DNA or RNA for replication.
Instead, they “reproduce” by inducing existing normal proteins ($PrP^C$) to misfold.
This conformational change converts the normal protein into the infectious form ($PrP^{Sc}$).
The amino acid sequence remains identical; only the three-dimensional shape changes.
This process triggers a chain reaction, leading to protein aggregation and brain damage.

Question

At which one of these points of time do the proteins coded for by genes in a multigene family begin to evolve distinct functions?

a. when gene duplication occurs
b. when exon shuffling occurs
c. when the genes are expressed by transcription and translation
d. when different mutations occur in each protein-coding sequence

▶️ Answer/Explanation

Detailed solution

The correct answer is d.
A multigene family starts with a gene duplication event, creating two identical copies.
Evolutionary divergence only begins when independent mutations accumulate in the sequences.
These mutations alter the amino acid sequence, leading to distinct protein functions.
Duplication (option a) provides the raw material but does not itself create functional variety.
Transcription and translation (option c) merely express the existing genetic code.
Therefore, mutational divergence is the specific point where functions start to differ.

Question

If a single base-insertion mutation occurred within the first exon of a eukaryotic gene, which of the following would be the likely result?

a. improper splicing by spliceosome

b. a longer mature mRNA

c. a failure of the initiation of translation

d. a silent mutation

▶️ Answer/Explanation

Detailed solution

The correct answer is b. a longer mature mRNA.
An insertion adds a nucleotide base to the DNA sequence, which is then transcribed into the pre-mRNA.
Exons are the coding regions that are retained and joined together during the process of RNA splicing.
Because the mutation occurs within an exon, the extra base remains in the final transcript.

Spliceosomes recognize specific sequences at intron-exon boundaries, which are usually unaffected by internal exon insertions.
Translation initiation typically depends on the $5’$ cap and start codon, which remain functional.
A single base insertion shifts the reading frame, making a silent mutation ($d$) virtually impossible.

Pre AP Biology -GEN 3.4 Mutations- MCQ Exam Style Questions -New Syllabus