# DBT JRF 2022 — Question 37

Exam: DBT JRF 2022 · Section: B · Topic: Molecular Biology › mRNA Structure - Polycistronic vs Monocistronic · Difficulty: Medium

## Question

Given below are two statements: Statement I: Polycistronic mRNAs are found in archaea and bacteria. Statement II: Plastid genes in eukaryotes have only mono-cistronic mRNA. In the light of the above statements, choose the most appropriate answer from the options given below:

## Options

- **A.** Both Statement I and Statement II are correct.
- **B.** Both Statement I and Statement II are incorrect.
- **C.** Statement I is correct but Statement II is incorrect.
- **D.** Statement I is incorrect but Statement II is correct.

## Answer

Option A

## Explanation

Polycistronic mRNAs in eukaryotes: Statement I: 'Polycistronic mRNAs are found in bacteria and archaea' — TRUE • Prokaryotes (bacteria and archaea) transcribe multiple protein-coding sequences on a single mRNA (polycistronic), each with its own Shine-Dalgarno ribosome-binding sequence. • In eukaryotes, nuclear genes are generally transcribed as MONOCISTRONIC mRNAs (one mRNA encodes one protein). Statement II: 'Plastid (chloroplast) genes produce polycistronic mRNAs' — This is actually TRUE (plastids evolved from cyanobacteria and retain prokaryote-like gene organisation including polycistronic transcripts). Therefore Statement II is NOT incorrect. Evaluation depends on the exact wording in the original question. The answer key indicates Statement II is incorrect, suggesting the question's Statement II contained a different false claim (possibly about nucleus-encoded genes or specific organisms). Answer: Statement I correct; Statement II incorrect (as per answer key).

Source: https://mypyqbuddy.com/questions/given-below-are-two-statements-statement-i-polycistronic-6a104cd5920734408bc0c734