Pre AP Biology -GEN 3.1 RNA Structure- MCQ Exam Style Questions -New Syllabus

Pre AP Biology -GEN 3.1 RNA Structure- MCQ Exam Style Questions – New Syllabus 2025-2026

Pre AP Biology -GEN 3.1 RNA Structure- MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.

Pre AP Biology – MCQ Exam Style Questions- All Topics

Question

A novel compound called NOBA is a zinc finger inhibitor. That is, NOBA destroys the function of zinc fingers by pulling the zinc ions away. Which of these components of gene expression is most likely to be directly inhibited by NOBA?

a. enhancer
b. poly(A) polymerase
c. DNA-binding protein
d. miRNA

▶️ Answer/Explanation

Detailed solution

The correct option is c. DNA-binding protein.
Zinc fingers are structural motifs characterized by the coordination of one or more $Zn^{2+}$ ions.
These motifs are primarily found in transcription factors, which are a type of DNA-binding protein.
The $Zn^{2+}$ ion stabilizes the “finger” structure, allowing the protein to fit into the major groove of DNA.
If NOBA removes the $Zn^{2+}$ ions, the protein loses its specific 3D conformation.
Without this shape, the protein can no longer bind to its target DNA sequences effectively.
This directly inhibits the function of the DNA-binding protein in regulating gene expression.

Question

Imagine a mutation in the E. coli lac operon that results in constitutive expression (always on). Further analysis confirms that normal amounts of functional lac repressor protein are present. Where must the mutation be?

a. in the lac promoter

b. in the operator

c. in the lacZ gene

d. in the CAP binding site

▶️ Answer/Explanation

Detailed solution

The correct answer is b. in the operator.
Constitutive expression means the genes are transcribed continuously regardless of lactose levels.
Since functional repressor protein is present, the lacI gene is not the site of the mutation.
A mutation in the operator ($O^c$) prevents the repressor protein from recognizing or binding to the DNA site.
Without repressor binding, RNA polymerase has unimpeded access to the promoter.
This leads to “always on” transcription of the structural genes like lacZ.
Mutations in the promoter or CAP site would typically decrease or prevent transcription rather than increase it.

Question

Which of these statements applies to $\text{miRNA}$?

a. It is encoded by non–protein-coding genes.

b. It has a precursor that is folded and then elongated by a Dicer enzyme.

c. It forms complementary base pairs with $\text{tRNA}$.

d. It is translated in the cytoplasm.

▶️ Answer/Explanation

Detailed solution

The correct option is a.
$\text{miRNA}$ (microRNA) molecules are transcribed from DNA but do not code for proteins.
They are functional RNA molecules that regulate gene expression post-transcriptionally.
The Dicer enzyme actually cleaves or cuts the precursor $\text{RNA}$, rather than elongating it.
$\text{miRNA}$ typically forms complementary base pairs with $\text{mRNA}$, not $\text{tRNA}$.
As non-coding $\text{RNA}$, $\text{miRNA}$ is never translated into a polypeptide chain.
Therefore, it is strictly classified as being encoded by non–protein-coding genes.

Pre AP Biology -GEN 3.1 RNA Structure- MCQ Exam Style Questions -New Syllabus