Gene Expression and Regulation Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Gene Expression and Regulation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Gene Expression and Regulation Indian Medical PG Question 1: Which of the following statements is NOT applicable to bacterial genomes?
- A. It is composed of DNA
- B. It does not contain histones
- C. It is circular
- D. Its DNA has both introns and exons (Correct Answer)
Gene Expression and Regulation Explanation: ***Its DNA has both introns and exons***
- **Bacterial genomes** are typically organized as continuous coding sequences and **lack introns** (non-coding regions) that are characteristic of eukaryotic genes.
- The presence of introns and their subsequent splicing is a hallmark of **eukaryotic gene expression**, not prokaryotic.
*It is composed of DNA*
- The genetic material of bacteria, like all cellular life forms, is primarily composed of **DNA (deoxyribonucleic acid)**.
- DNA serves as the blueprint for all cellular processes and hereditary information.
*It does not contain histones*
- **Bacterial DNA** is typically compacted by various DNA-binding proteins, but these are not the **histone proteins** found in eukaryotes.
- Histones are fundamental for packaging DNA into **chromatin** in eukaryotic cells.
*It is circular*
- The main chromosome in most bacteria is **covalently closed** and **circular**, unlike the linear chromosomes found in eukaryotes.
- This circular structure aids in replication and stability within the bacterial cell.
Gene Expression and Regulation Indian Medical PG Question 2: Which of the following is considered a fundamental defense mechanism in psychology?
- A. Alienation
- B. Confabulation
- C. Repression (Correct Answer)
- D. Suppression
Gene Expression and Regulation Explanation: ***Repression***
- **Repression** is the **fundamental unconscious defense mechanism** where unacceptable thoughts, feelings, or memories are pushed out of conscious awareness to protect the ego.
- It is considered the foundational defense mechanism because it operates automatically and without conscious effort, forming the basis for many other defense mechanisms.
*Alienation*
- **Alienation** refers to a feeling of estrangement or disconnection from others, society, or oneself, often due to social or psychological factors, but it is not a defense mechanism.
- It describes a state of being rather than an active psychological process used to cope with anxiety.
*Confabulation*
- **Confabulation** is the creation of false autobiographical memories without the intent to deceive, often seen in neurological conditions like **Korsakoff's syndrome**.
- It is a symptom of memory impairment, not an active psychological defense mechanism.
*Suppression*
- **Suppression** is a defense mechanism but is considered a mature/conscious defense; it involves deliberately and consciously putting unwanted thoughts or feelings out of mind.
- Unlike **repression**, **suppression** is an intentional and relatively aware act of avoiding disturbing thoughts.
Gene Expression and Regulation Indian Medical PG Question 3: If the percentage of thymine residues in DNA is 28%. What is the percentage of cytosine?
- A. 36%
- B. 44%
- C. 22% (Correct Answer)
- D. 28%
Gene Expression and Regulation Explanation: ***22%***
- According to **Chargaff's rules**, in a DNA molecule, the amount of **adenine (A) is equal to the amount of thymine (T)**, and the amount of **guanine (G) is equal to the amount of cytosine (C)**.
- If thymine (T) is 28%, then adenine (A) is also 28%, making a total of 56% for A+T. The remaining 44% (100% - 56%) is split equally between guanine and cytosine, so cytosine (C) is 22%.
*36%*
- This percentage would be plausible if the sum of adenine and thymine were 28%, which is incorrect as A and T are equal and their sum would thus be 56%.
- This value does not adhere to the principle of **base pairing complementarity** and the total percentage of all bases summing to 100%.
*44%*
- This would be the combined percentage of guanine and cytosine, not the percentage of cytosine alone.
- If cytosine were 44%, then guanine would also be 44%, leading to a total of 88% for G+C, which is inconsistent with T being 28%.
*28%*
- This is the percentage of thymine, and by **Chargaff's rules**, it would also be the percentage of adenine, not cytosine.
- Cytosine percentages are derived from the remaining proportion of bases after accounting for adenine and thymine.
Gene Expression and Regulation Indian Medical PG Question 4: Which type of mutation can act as a suppressor to restore the wild-type phenotype in organisms carrying a mutant gene?
- A. Frameshift mutation of coding gene
- B. Mutation of tRNA (Correct Answer)
- C. Deletion of mutant gene
- D. Addition of another normal gene
Gene Expression and Regulation Explanation: ***Mutation of tRNA***
- A **tRNA suppressor mutation** can alter its anticodon, allowing it to recognize a **stop codon** (nonsense suppressor) or a missense codon, and insert an amino acid, thereby suppressing the original mutation.
- This is a classic example of an **intergenic suppressor mutation** that acts at a different genetic locus from the original mutation.
- These suppressors are particularly effective for **nonsense mutations** (premature stop codons) and certain missense mutations by correcting the decoding error during translation.
*Frameshift mutation of coding gene*
- A single frameshift mutation causes a shift in the **reading frame**, leading to a completely different protein sequence downstream and often a premature stop codon, which would worsen the phenotype.
- While a **second compensating frameshift** mutation in the same gene could theoretically restore the reading frame (acting as an intragenic suppressor), this is context-dependent and less reliable than tRNA suppressors.
- The question asks for mutations that "can act as a suppressor," and **tRNA mutations are the more universally recognized and reliable suppressor mechanism** in classical genetics.
*Deletion of mutant gene*
- **Deleting the mutant gene** removes the genetic information entirely but does not restore wild-type function; instead, it typically results in **loss of function** or complete absence of the protein.
- This would lead to a **null phenotype** rather than restoration of wild-type phenotype, especially if the gene is essential.
*Addition of another normal gene*
- The **addition of another normal (wild-type) gene copy** provides a functional protein that can compensate for the mutant gene's deficiency.
- While this can restore a wild-type phenotype, it represents **gene complementation** or gene therapy, not a true suppressor mutation that modifies the interpretation or expression of the existing mutant allele.
Gene Expression and Regulation Indian Medical PG Question 5: Which type of RNA is primarily involved in gene silencing?
- A. rRNA
- B. tRNA
- C. miRNA (Correct Answer)
- D. mRNA
Gene Expression and Regulation Explanation: ***miRNA***
- **miRNA** (microRNA) is a small non-coding RNA molecule that plays a crucial role in **post-transcriptional regulation of gene expression**.
- It functions by binding to complementary messenger RNA (mRNA) molecules, leading to **mRNA degradation** or **inhibition of translation**, thereby silencing genes.
- miRNA is the primary RNA type involved in **gene silencing** through the RNA interference (RNAi) pathway.
*rRNA*
- **rRNA** (ribosomal RNA) is a primary component of **ribosomes**, the cellular machinery responsible for protein synthesis.
- Its main function is to **catalyze peptide bond formation** and provide structural integrity to the ribosome, not gene silencing.
*tRNA*
- **tRNA** (transfer RNA) is responsible for carrying specific **amino acids** to the ribosome during protein synthesis.
- It acts as an adapter molecule, translating the **genetic code** in mRNA into an amino acid sequence.
*mRNA*
- **mRNA** (messenger RNA) carries genetic information from **DNA to ribosomes** for protein synthesis.
- While mRNA can be targeted by gene silencing mechanisms (like miRNA), it is not the RNA type that performs the silencing function itself.
Gene Expression and Regulation Indian Medical PG Question 6: Assertion: DNA methylation leads to gene silencing. Reason: Methylation prevents binding of transcription factors to promoter regions.
- A. Assertion is true but reason is false.
- B. Both assertion and reason are true and reason is the correct explanation. (Correct Answer)
- C. Both assertion and reason are true but reason is not the correct explanation.
- D. Both assertion and reason are false.
Gene Expression and Regulation Explanation: ***Both assertion and reason are true and reason is the correct explanation.***
- **DNA methylation** at **CpG islands** in promoter regions is a well-established **epigenetic mechanism for gene silencing**
- The reason directly explains HOW methylation causes silencing: **methylation prevents transcription factor binding** to promoter regions, blocking transcriptional machinery
- Both statements are factually correct AND the reason provides the mechanistic explanation for the assertion
*Assertion is true but reason is false.*
- While the assertion is correct (DNA methylation does lead to gene silencing), the reason is also TRUE, not false
- Methylation preventing transcription factor binding is indeed a **primary mechanism** of gene silencing
- This option would only be correct if the reason statement were factually incorrect
*Both assertion and reason are true but reason is not the correct explanation.*
- Both statements are individually true, but this option is incorrect because the reason IS the correct explanation
- The prevention of transcription factor binding **directly explains** how methylation silences genes
- If this were correct, the reason would describe an unrelated consequence of methylation, not the causal mechanism
*Both assertion and reason are false.*
- Both statements are well-established biological facts
- DNA methylation-mediated gene silencing is a fundamental epigenetic mechanism
- Prevention of transcription factor binding is a validated mechanism of this silencing
Gene Expression and Regulation Indian Medical PG Question 7: What is the technique for accurate quantification of gene expression?
- A. PCR
- B. Real-Time Reverse Transcriptase PCR (Correct Answer)
- C. Reverse Transcriptase PCR
- D. Northern blot
Gene Expression and Regulation Explanation: ***Real-Time Reverse Transcriptase PCR***
- This technique allows for the **quantification of gene expression** by concurrently reverse-transcribing RNA to cDNA and amplifying it while monitoring the accumulation of DNA in real-time using fluorescent reporters.
- The ** threshold cycle (Ct) value** is inversely proportional to the initial amount of target mRNA, enabling precise quantification.
*Northern blot*
- This method is used to detect **RNA sequences** and can provide semi-quantitative data about gene expression levels based on band intensity.
- However, it is generally **less sensitive** and provides less precise quantification compared to real-time PCR.
*PCR*
- **Standard PCR** amplifies DNA, but it is not directly used for gene expression quantification as it starts with DNA templates.
- While it can be used to detect the presence of a gene, it does not quantify its expression without further modifications or additional steps like reverse transcription and real-time monitoring.
*Reverse Transcriptase PCR*
- This technique involves **reverse transcribing RNA into cDNA** and then performing standard PCR to amplify the cDNA.
- While it confirms the presence of mRNA and allows for cDNA amplification, it is a **qualitative or semi-quantitative** method for expression, as the endpoint detection does not accurately reflect initial mRNA concentration due to plateau effects.
Gene Expression and Regulation Indian Medical PG Question 8: Recombinant human insulin is made by -
- A. cDNA of pancreatic cell (Correct Answer)
- B. cDNA from any eukaryote cell
- C. Genome of pancreatic cell
- D. Genome of any eukaryote
Gene Expression and Regulation Explanation: ***CDNA of pancreatic cell***
- **Recombinant human insulin** is produced using **cDNA** (complementary DNA) synthesized from the **mRNA** of human pancreatic cells, as these cells naturally produce insulin.
- This cDNA ensures that only the **coding sequences** for insulin are used, without introns, making it suitable for expression in prokaryotic hosts like *E. coli*.
*CDNA from any eukaryote cell*
- While insulin is a eukaryotic protein, using cDNA from "any eukaryote cell" would not be specific enough, as only **pancreatic islet beta cells** produce insulin.
- Other eukaryotic cells do not express the insulin gene, so their cDNA would not contain the necessary genetic information.
*Genome of pancreatic cell*
- Although the **genome of a pancreatic cell** contains the insulin gene, it also includes **introns** (non-coding regions) that must be removed through splicing in eukaryotic cells.
- If directly used in prokaryotic systems (like *E. coli*), which lack the machinery to remove introns, it would lead to an incorrect or non-functional protein.
*Genome of any eukaryote*
- Similar to "genome of pancreatic cell," using the **genome of any eukaryote** would be problematic due to the presence of introns and the general lack of the insulin gene in most eukaryotic cells.
- This option combines the disadvantages of non-specificity and the presence of introns that are incompatible with prokaryotic expression systems.
Gene Expression and Regulation Indian Medical PG Question 9: What is Northern blot used to detect?
- A. Protein
- B. Immunoglobulin
- C. RNA (Correct Answer)
- D. DNA
Gene Expression and Regulation Explanation: ***RNA***
- **Northern blot** is a laboratory technique used to detect specific **RNA** molecules among a mixture of RNA.
- It involves separating RNA fragments by **gel electrophoresis**, transferring them to a membrane, and then probing with a labeled complementary sequence.
*Protein*
- **Proteins** are typically detected using a **Western blot**, which involves similar separation and transfer techniques but uses **antibodies** as probes.
- While RNA codes for proteins, Northern blot *directly* detects RNA transcripts, not the resulting protein products.
*Immunoglobulin*
- **Immunoglobulins** (antibodies) are a type of protein, and their detection usually falls under **Western blot** or specific immunological assays like **ELISA**.
- Northern blot is specifically designed for nucleic acid analysis, not protein detection.
*DNA*
- **DNA** is detected using a **Southern blot** technique, which also involves electrophoresis, transfer to a membrane, and hybridization with a complementary probe.
- The name "Northern blot" was coined as a play on "Southern blot" because it uses similar methodology but for RNA instead of DNA.
Gene Expression and Regulation Indian Medical PG Question 10: Effect of environment on genes is called?
- A. Euthenics
- B. Positive Eugenics
- C. Negative Eugenics
- D. Epigenetics (Correct Answer)
Gene Expression and Regulation Explanation: ***Epigenetics***
- **Epigenetics** refers to heritable changes in **gene expression** that do not involve alterations to the underlying **DNA sequence**.
- These changes are often influenced by **environmental factors**, such as diet, stress, and exposure to toxins, which can affect how genes are turned on or off.
*Positive Eugenics*
- **Positive eugenics** aims to improve the human population by encouraging the reproduction of individuals deemed to have "desirable" traits.
- This concept is ethically controversial and focuses on directed breeding rather than environmental gene influence.
*Negative Eugenics*
- **Negative eugenics** aims to reduce the prevalence of "undesirable" traits in the human population by discouraging or preventing the reproduction of individuals deemed to possess them.
- Like positive eugenics, this is a highly controversial concept focused on limiting reproduction based on perceived genetic quality.
*Euthenics*
- **Euthenics** is a movement focused on improving human well-being and development by improving living conditions and the environment.
- While it acknowledges the impact of the environment, it focuses on societal and lifestyle improvements rather than the direct molecular changes in gene expression.
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