Nucleic Acid Biochemistry Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Nucleic Acid Biochemistry. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Nucleic Acid Biochemistry Indian Medical PG Question 1: Which type of RNA contains codons for specific amino acids?
- A. Transfer RNA (tRNA)
- B. Messenger RNA (mRNA) (Correct Answer)
- C. Small nuclear RNA (snRNA)
- D. Ribosomal RNA (rRNA)
Nucleic Acid Biochemistry Explanation: ***Messenger RNA (mRNA)***
- **mRNA** carries the genetic information from **DNA** in the nucleus to the **ribosomes** in the cytoplasm.
- This information is encoded in sequences of three nucleotides called **codons**, each specifying a particular amino acid.
*Transfer RNA (tRNA)*
- **tRNA** molecules are responsible for **carrying specific amino acids** to the ribosome during protein synthesis.
- Each **tRNA** has an **anticodon** that base-pairs with a complementary **codon** on the **mRNA** strand.
*Small nuclear RNA (snRNA)*
- **snRNA** is primarily involved in **RNA splicing**, a process that removes introns from pre-mRNA.
- It forms part of the **spliceosome** complex, which is crucial for mature mRNA formation but does not contain codons itself.
*Ribosomal RNA (rRNA)*
- **rRNA** is a major component of **ribosomes**, the cellular machinery responsible for protein synthesis.
- While it plays a critical structural and catalytic role in translation, it does not carry genetic code in the form of codons.
Nucleic Acid Biochemistry Indian Medical PG Question 2: Which diagnostic tool is preferred for metabolic disease screening in children?
- A. Urinalysis
- B. Genetic testing
- C. Complete Blood count
- D. Tandem mass spectrometry (Correct Answer)
- E. Plasma amino acid analysis
Nucleic Acid Biochemistry Explanation: ***Tandem mass spectrometry***
- **Tandem mass spectrometry (TMS)** is the preferred method for newborn screening of many **inborn errors of metabolism** because it can simultaneously detect a wide range of metabolites from a single dried blood spot.
- This technique rapidly identifies multiple **amino acid disorders**, **fatty acid oxidation disorders**, and **organic acidemias**, allowing for early intervention.
*Urinalysis*
- While urinalysis can detect some metabolic abnormalities (e.g., **ketones**, **glucose**), it is not a comprehensive screening tool for the broad spectrum of inherited metabolic diseases.
- It primarily identifies end-products of metabolism rather than specific enzyme deficiencies or precursor compounds.
*Genetic testing*
- **Genetic testing** is highly specific for known genetic mutations, but it is typically used for confirmatory diagnosis or targeted screening when a specific condition is suspected, not for broad, universal newborn metabolic screening.
- It can be expensive and time-consuming for population-wide screening of hundreds of potential metabolic disorders.
*Complete Blood count*
- A **complete blood count (CBC)** assesses cellular components of the blood (e.g., **red blood cells**, **white blood cells**, **platelets**) and is useful for detecting hematological disorders.
- It does not directly screen for metabolic diseases, although some metabolic disorders can secondarily affect blood cell counts.
*Plasma amino acid analysis*
- **Plasma amino acid analysis** can detect specific aminoacidopathies (e.g., **phenylketonuria**, **maple syrup urine disease**), but it is limited to amino acid disorders only.
- Unlike tandem mass spectrometry, it cannot simultaneously screen for fatty acid oxidation disorders and organic acidemias, making it less comprehensive for broad metabolic screening.
Nucleic Acid Biochemistry Indian Medical PG Question 3: Which of the following is not a component of a nucleotide?
- A. Sugar
- B. Fatty acid (Correct Answer)
- C. Base
- D. Phosphate
Nucleic Acid Biochemistry Explanation: ***Fatty acid***
- A **fatty acid** is a component of **lipids**, such as triglycerides and phospholipids, which are structurally and functionally distinct from **nucleotides**.
- **Nucleotides** are the building blocks of nucleic acids (DNA and RNA), whereas fatty acids are essential for cell membranes and energy storage.
*Sugar*
- A **pentose sugar** (either **deoxyribose** in DNA or **ribose** in RNA) is a fundamental component of every nucleotide.
- This sugar forms the backbone of the nucleic acid strand, covalently linked to the phosphate group and the nitrogenous base.
*Phosphate*
- A **phosphate group** is a crucial component of a nucleotide, providing the negative charge and forming the phosphodiester bonds that link nucleotides together into a nucleic acid chain.
- The number of phosphate groups (mono-, di-, or triphosphate) determines the nucleotide's energy state and function.
*Base*
- A **nitrogenous base** (adenine, guanine, cytosine, thymine, or uracil) is an essential component of a nucleotide, responsible for genetic information storage and pairing.
- This base is attached to the pentose sugar and determines the specific identity of the nucleotide within the DNA or RNA sequence.
Nucleic Acid Biochemistry Indian Medical PG Question 4: Identify the gene commonly involved in the condition shown in the image?
- A. RAS
- B. RET
- C. BRAF V600E (Correct Answer)
- D. P53
Nucleic Acid Biochemistry Explanation: ***BRAF V600E***
- The image displays cells with **Langerhans cell morphology**, including folded nuclei and abundant pale cytoplasm, which are characteristic of **Langerhans cell histiocytosis (LCH)** [1].
- The **BRAF V600E mutation** is the most common genetic alteration found in LCH, present in about 50-60% of cases and activating the MAPK pathway [1].
*RAS*
- **RAS mutations** are frequently seen in various cancers, including colorectal adenocarcinoma, pancreatic adenocarcinoma, and non-small cell lung cancer.
- While RAS pathway activation can occur in LCH, a direct RAS mutation is not the most common genetic driver; rather, downstream effectors like BRAF V600E are more prominent [1].
*RET*
- **RET mutations** are primarily associated with **medullary thyroid carcinoma** (in both sporadic and inherited forms like MEN 2A and MEN 2B) and can also be found in certain types of lung cancer.
- They are not a characteristic genetic alteration for Langerhans cell histiocytosis.
*P53*
- The **TP53 gene** encodes the tumor suppressor protein p53, and mutations in this gene are among the most frequent genetic alterations across a wide spectrum of human cancers.
- Although p53 plays a critical role in cell cycle regulation and apoptosis, it is not a primary or common driver mutation specifically associated with Langerhans cell histiocytosis [1].
**References:**
[1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 629-630.
Nucleic Acid Biochemistry Indian Medical PG Question 5: Which of the following correctly describes gene therapy ?
- A. Mapping and isolation of gene sequence
- B. Introduction of gene sequence into a cell (Correct Answer)
- C. Synthesis of DNA probes with specific sequence
- D. Use of polymerase chain reaction technique
Nucleic Acid Biochemistry Explanation: ***Introduction of gene sequence into a cell***
- **Gene therapy** fundamentally involves the **delivery of genetic material** (DNA or RNA) into a patient's cells to treat or prevent disease.
- The goal is to correct a **genetic defect**, provide a new therapeutic function, or alter gene expression for a desired outcome.
*Mapping and isolation of gene sequence*
- While essential steps in understanding and preparing for gene therapy, **mapping and isolation** alone do not constitute the therapy itself.
- These processes are preliminary research activities to identify the target gene and its location.
*Synthesis of DNA probes with specific sequence*
- **DNA probes** are short, single-stranded DNA or RNA sequences used to detect the presence of complementary nucleic acid sequences.
- Their synthesis is a technique used in **molecular diagnostics** and research, not gene therapy, which aims to introduce functional genes.
*Use of polymerase chain reaction technique*
- **PCR** is a molecular biology technique used to amplify a specific segment of DNA, creating many copies.
- It is a tool for **diagnosis**, research, and sometimes in the preparation of genetic material for therapy, but it is not gene therapy itself.
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