(A) an activator or a repressor
(B) an RNA or a protein
(C) a protein with the same or different amino acids
(D) a diffusible or non-diffusible product
The cis-trans test distinguishes whether mutations affect diffusible gene products like proteins or non-diffusible cis-acting elements. This SEO article covers Q.73 with the correct answer and all options for genetics exam prep.
Correct Answer
The correct answer is (D) a diffusible or non-diffusible product.
In trans configuration (mutations on separate chromosomes), diffusible products (proteins) from one wild-type gene complement the other mutant, restoring wild-type phenotype. Cis configuration (both mutations on same chromosome) serves as control. No complementation in trans indicates non-diffusible cis-acting elements.
Option Breakdowns
(A) an activator or a repressor
Cis-trans test identifies complementation between genes, not activator/repressor function.
Regulatory protein classification requires functional assays.
(B) an RNA or a protein
Test distinguishes functional units (cistrons), not RNA vs protein products.
Both can be diffusible; test doesn’t discriminate product type.
(C) a protein with the same or different amino acids
Test determines if mutations are in same vs different genes, not amino acid identity.
Sequencing analyzes specific changes.
(D) a diffusible or non-diffusible product
Classic Benzer rII phage test: trans complementation = diffusible proteins; no complementation = cis-acting DNA elements.
Defines one gene-one enzyme concept.
| Option | Test Capability | Cis-Trans Function | Matches Q.73? |
|---|---|---|---|
| (A) Activator/repressor | No | Complementation only | No |
| (B) RNA/protein | No | Product class irrelevant | No |
| (C) Amino acid changes | No | Gene separation only | No |
| (D) Diffusible/non-diffusible | Yes | Core principle | Yes |
