Transcription: RNA Synthesis Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Transcription: RNA Synthesis. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Transcription: RNA Synthesis Indian Medical PG Question 1: In E. coli, Arthur Kornberg found which enzyme?
- A. DNA polymerase (Correct Answer)
- B. Glucose 6 phosphate dehydrogenase
- C. Fatty acid synthase
- D. Topoisomerase
Transcription: RNA Synthesis Explanation: ***DNA polymerase***
- Arthur Kornberg was awarded the Nobel Prize in Physiology or Medicine in 1959 for his discovery of **DNA polymerase I** in *Escherichia coli*.
- This enzyme is crucial for **DNA replication and repair** in bacteria, catalyzing the synthesis of new DNA strands.
*Fatty acid synthase*
- This enzyme complex is responsible for the **biosynthesis of fatty acids** in living organisms.
- While essential for *E. coli*, its discovery is not attributed to Arthur Kornberg.
*Glucose 6 phosphate dehydrogenase*
- This enzyme is key in the **pentose phosphate pathway**, producing NADPH and ribose-5-phosphate.
- It is critical for cellular metabolism but was not the enzyme discovered by Kornberg.
*Topoisomerase*
- Topoisomerases are enzymes that regulate the **supercoiling of DNA** by transiently breaking and rejoining DNA strands.
- Their discovery postdates Kornberg's work on DNA polymerase.
Transcription: RNA Synthesis Indian Medical PG Question 2: Which RNA modification at the 3' end stabilizes mRNA by preventing exonuclease degradation?
- A. Polyadenylation (Correct Answer)
- B. Capping
- C. Splicing
- D. Methylation
Transcription: RNA Synthesis Explanation: ***Polyadenylation***
- The addition of a **poly-A tail** (a long chain of adenine nucleotides) to the **3' end** of mRNA is the primary modification that protects it from degradation by **3' to 5' exonucleases**.
- This tail also plays crucial roles in mRNA export from the nucleus, translation initiation, and determining mRNA half-life.
- The poly-A tail is progressively shortened by deadenylases, and once critically shortened, the mRNA becomes susceptible to degradation.
*Capping*
- **5' capping** involves the addition of a **7-methylguanosine cap** to the **5' end** of mRNA.
- While this protects mRNA from **5' to 3' exonuclease** degradation, the question specifically asks about the **3' end** modification, which is polyadenylation.
- The cap structure is also essential for ribosome binding and translation initiation.
*Splicing*
- **Splicing** is the process of removing **introns** (non-coding regions) and joining **exons** (coding regions) in pre-mRNA.
- Its main function is to produce a mature mRNA sequence that can be translated into a functional protein, not to directly prevent exonuclease degradation.
*Methylation*
- **Methylation** can occur on various nucleotides within RNA molecules (e.g., N6-methyladenosine or m6A).
- While methylation can influence mRNA stability, translation efficiency, and splicing, it is primarily a regulatory modification rather than a direct structural protection against exonuclease degradation like polyadenylation.
Transcription: RNA Synthesis Indian Medical PG Question 3: A lady gets pregnant even though she was on contraceptive pills. She is suspected to have consumed
- A. Ciprofloxacin
- B. Rifampicin (Correct Answer)
- C. Streptomycin
- D. None of these
Transcription: RNA Synthesis Explanation: ***Rifampicin***
- **Rifampicin** is a potent inducer of **hepatic microsomal enzymes** (cytochrome P450 enzymes), particularly CYP3A4.
- This enzyme induction leads to increased metabolism and thus decreased effectiveness of **oral contraceptive pills**, raising the risk of unintended pregnancy.
*Ciprofloxacin*
- **Ciprofloxacin** is a **quinolone antibiotic** that primarily works by inhibiting bacterial DNA gyrase and topoisomerase IV.
- It does not significantly induce hepatic enzymes or interfere with the efficacy of **oral contraceptive pills**.
*Streptomycin*
- **Streptomycin** is an **aminoglycoside antibiotic** that inhibits bacterial protein synthesis.
- It is not known to have a significant drug interaction with **oral contraceptive pills** that would lead to contraceptive failure.
*None of these*
- This option is incorrect because **Rifampicin** is well-documented to reduce the effectiveness of **oral contraceptive pills**.
Transcription: RNA Synthesis Indian Medical PG Question 4: Match the following drugs in Column A with their contraindications in Column B.
| Column A | Column B |
| :-- | :-- |
| 1. Morphine | 1. QT prolongation |
| 2. Amiodarone | 2. Thromboembolism |
| 3. Vigabatrin | 3. Pregnancy |
| 4. Estrogen preparations | 4. Head injury |
- A. A-1, B-3, C-2, D-4
- B. A-4, B-1, C-3, D-2 (Correct Answer)
- C. A-3, B-2, C-4, D-1
- D. A-2, B-4, C-1, D-3
Transcription: RNA Synthesis Explanation: ***A-4, B-1, C-3, D-2***
- **Morphine** is contraindicated in **head injury** as it can increase intracranial pressure and mask neurological symptoms.
- **Amiodarone** is contraindicated in patients with **QT prolongation** due to its risk of inducing more severe arrhythmias like Torsades de Pointes.
- **Vigabatrin** is contraindicated during **pregnancy** due to its potential for teratogenicity and adverse effects on fetal development.
- **Estrogen preparations** are contraindicated in patients with a history of **thromboembolism** due to their increased risk of blood clot formation.
*A-1, B-3, C-2, D-4*
- This option incorrectly matches **Morphine** with QT prolongation and **Estrogen preparations** with head injury, which are not their primary contraindications.
- It also incorrectly links **Vigabatrin** with thromboembolism and **Amiodarone** with pregnancy.
*A-3, B-2, C-4, D-1*
- This choice incorrectly associates **Morphine** with pregnancy and **Vigabatrin** with head injury, which are not the most critical or direct contraindications.
- It also misaligns **Amiodarone** with thromboembolism and **Estrogen preparations** with QT prolongation.
*A-2, B-4, C-1, D-3*
- This option incorrectly matches **Morphine** with thromboembolism and **Amiodarone** with head injury, which are not their most significant contraindications.
- It also incorrectly links **Vigabatrin** with QT prolongation and **Estrogen preparations** with pregnancy.
Transcription: RNA Synthesis Indian Medical PG Question 5: Steps in review of patient's history during secondary survey of trauma care can be summarised as
- A. TRIAGE
- B. ABCDE
- C. AMPLE (Correct Answer)
- D. None of the options
Transcription: RNA Synthesis Explanation: ***AMPLE***
- The **AMPLE history** is a mnemonic used during the **secondary survey** in trauma care to gather crucial patient information
- It stands for **Allergies, Medications, Past medical history/Pregnancy, Last meal, and Events** surrounding the injury.
*TRIAGE*
- **Triage** is the process of prioritizing patients based on the severity of their condition and the likelihood of benefit from immediate treatment.
- It is an initial assessment done to determine the urgency of care, not a detailed historical review for a single patient.
*ABCDE*
- The **ABCDE approach** (**Airway, Breathing, Circulation, Disability, Exposure**) is part of the **primary survey** in trauma care.
- It focuses on identifying and managing immediate life-threatening conditions.
*None of the options*
- This option is incorrect because **AMPLE** specifically describes the historical review process during the secondary survey.
Transcription: RNA Synthesis Indian Medical PG Question 6: Which of the following statements about Taq DNA polymerase is correct?
- A. Optimum temperature for chain elongation is 75°C (Correct Answer)
- B. Denatures at high temperatures
- C. Provides high fidelity during DNA synthesis
- D. Exhibits 3' to 5' exonuclease activity
Transcription: RNA Synthesis Explanation: ***Optimum temperature for chain elongation is 75°C***
- **Taq polymerase** is a **thermostable enzyme** isolated from *Thermus aquaticus*, functioning optimally at high temperatures.
- The optimal temperature for the **elongation step** in PCR, where Taq polymerase synthesizes new DNA strands, is typically around **72-78°C**, with 75°C falling within this optimal range.
*Denatures at high temperatures*
- While all proteins will eventually denature at extremely high temperatures, Taq polymerase is specifically known for its **thermostability** and **resistance to denaturation** at temperatures required for DNA strand separation in PCR (typically 94-98°C).
- Its ability to withstand these high temperatures without significant loss of activity is its key advantage for use in **Polymerase Chain Reaction (PCR)**.
*Provides high fidelity during DNA synthesis*
- **Taq polymerase** is known for its relatively **low fidelity** due to the lack of 3' to 5' exonuclease activity (proofreading).
- This low fidelity results in a higher error rate during DNA synthesis compared to other polymerases with proofreading capabilities, leading to more **mutations** during PCR.
*Exhibits 3' to 5' exonuclease activity*
- **Taq polymerase** typically **lacks 3' to 5' exonuclease activity**, meaning it does not have the ability to proofread and remove incorrectly incorporated nucleotides.
- This absence of proofreading contributes to its relatively **lower fidelity** during DNA replication compared to other polymerases that possess this activity.
Transcription: RNA Synthesis Indian Medical PG Question 7: What sequence on the template strand of DNA corresponds to the first amino acid inserted into a protein?
- A. 3' TAC 5' (Correct Answer)
- B. 3' TAG 5'
- C. 3' TAA 5'
- D. 3' ATG 5'
Transcription: RNA Synthesis Explanation: ***3' TAC 5'***
- The **start codon** for protein synthesis on **mRNA** is **5'-AUG-3'**, which codes for **methionine** (or N-formylmethionine in prokaryotes) and signals the initiation of translation.
- To produce an mRNA codon of **5'-AUG-3'**, the complementary sequence on the **template DNA strand** must be **3'-TAC-5'** (adenine pairs with uracil/thymine, guanine pairs with cytosine, and the strands are antiparallel).
- During transcription, RNA polymerase reads the template strand in the 3' to 5' direction and synthesizes mRNA in the 5' to 3' direction.
*3' TAG 5'*
- This template DNA sequence would be transcribed to produce the mRNA codon **5'-AUC-3'**, which codes for **isoleucine**, not methionine.
- Therefore, this sequence does not correspond to the first amino acid inserted into a protein.
*3' TAA 5'*
- This template DNA sequence would be transcribed to produce the mRNA codon **5'-AUU-3'**, which also codes for **isoleucine**, not methionine.
- This is not the initiation codon sequence.
*3' ATG 5'*
- While **ATG** appears in this sequence, when presented as the **template strand** in the 3' to 5' orientation, it would be transcribed to produce mRNA **5'-UAC-3'**, which codes for **tyrosine**, not methionine.
- The sequence **ATG** on the **coding strand** (non-template strand) corresponds to the start codon, but this option incorrectly presents it as the template strand sequence.
Transcription: RNA Synthesis Indian Medical PG Question 8: Inosinic acid is biological precursor of ?
- A. Purines and thymine
- B. Orotic acid and uridylic acid
- C. Adenylic acid and guanylic acid (Correct Answer)
- D. Uracil and thymine
Transcription: RNA Synthesis Explanation: ***Adenylic acid and guanylic acid***
- Inosinic acid (IMP) is a **key intermediate** in the **de novo purine synthesis pathway**.
- It serves as the direct precursor for the synthesis of **adenylic acid (AMP)** and **guanylic acid (GMP)**, which are components of DNA and RNA.
*Purines and thymine*
- While inosinic acid is a precursor to purines, it is **not a precursor to thymine**.
- Thymine is a **pyrimidine base** and is synthesized through a separate pathway.
*Orotic acid and uridylic acid*
- **Orotic acid** is an intermediate in **pyrimidine synthesis**, not purine synthesis.
- **Uridylic acid (UMP)** is also a pyrimidine nucleotide, and its synthesis pathway involves orotic acid, not inosinic acid.
*Uracil and thymine*
- **Uracil** and **thymine** are pyrimidine bases, and their synthesis pathways are distinct from the purine synthesis pathway involving inosinic acid.
- Inosinic acid is exclusively involved in the synthesis of **purine nucleotides**.
Transcription: RNA Synthesis Indian Medical PG Question 9: Consider the following statements regarding folic acid :
1. It is needed for normal development of blood cells in the marrow.
2. It has a role in the synthesis of nucleic acids.
3. It is resistant to boiling.
Which of the statements given above is/are correct?
- A. 2 and 3
- B. 1 and 2 (Correct Answer)
- C. 1 and 3
- D. 1 only
Transcription: RNA Synthesis Explanation: ***Correct Answer: 1 and 2***
**Analysis of each statement:**
**Statement 1: Folic acid is needed for normal development of blood cells in the marrow** - **CORRECT**
- Folic acid is essential for **hematopoiesis** (blood cell formation)
- Required for normal maturation of **red blood cells** and **white blood cells**
- Deficiency leads to **megaloblastic anemia** due to impaired DNA synthesis in rapidly dividing cells
**Statement 2: Folic acid has a role in synthesis of nucleic acids** - **CORRECT**
- Acts as a coenzyme in **one-carbon transfer reactions**
- Essential for synthesis of **purines** and **thymidylate** (required for DNA synthesis)
- Critical for synthesis of both **DNA and RNA**
- Particularly important in rapidly dividing cells
**Statement 3: Folic acid is resistant to boiling** - **INCORRECT**
- Folic acid is **heat-labile** and **water-soluble**
- Destroyed by prolonged cooking and boiling
- Up to **50-90% loss** can occur during cooking of vegetables
- This is why fresh or lightly cooked vegetables are better sources of folate
**Why other options are incorrect:**
*Incorrect: 2 and 3*
- While statement 2 is correct, statement 3 is false - folic acid is NOT resistant to boiling
*Incorrect: 1 and 3*
- While statement 1 is correct, statement 3 is false - folic acid is heat-sensitive
*Incorrect: 1 only*
- Statement 2 is also correct - folic acid plays a fundamental role in nucleic acid synthesis
Transcription: RNA Synthesis Indian Medical PG Question 10: False statements are:
- A. DNA replication proceeds in one direction
- B. Lagging strand is synthesized by RNA primase
- C. All of the options (Correct Answer)
- D. Bacteria have multiple origins of replication
Transcription: RNA Synthesis Explanation: ***All of the options***
- All statements are **false**. DNA replication proceeds **bidirectionally**, bacteria typically have a **single origin of replication**, and the lagging strand is synthesized by **DNA polymerase** after an RNA primer is laid down by **RNA primase**.
*DNA replication proceeds in one direction*
- This statement is **false** because **DNA replication** is a **bidirectional process**, meaning it proceeds in both directions from the origin of replication.
- Replication forks move away from the **origin** on both sides, unraveling the DNA and synthesizing new strands.
*Bacteria have multiple origins of replication*
- This statement is **false**. Most **bacteria** (prokaryotes) have a **single origin of replication** (oriC) on their circular chromosome.
- In contrast, **eukaryotes** have **multiple origins of replication** on their linear chromosomes to replicate their much larger genomes efficiently.
- While rare exceptions exist in some bacterial species, the general rule for bacterial DNA replication is a single origin.
*Lagging strand is synthesized by RNA primase*
- This statement is **false**. The **lagging strand** is primarily synthesized by **DNA polymerase III** (in prokaryotes) or **DNA polymerase δ** (in eukaryotes).
- **RNA primase** is responsible for synthesizing short **RNA primers** that provide a starting point for DNA polymerase, but it does not synthesize the entire lagging strand itself.
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