Genetic organization of eukaryotes and prokaryotes MCQs With Answer

Introduction

Understanding the genetic organization of eukaryotes and prokaryotes is essential for B. Pharm students who study drug targets, gene expression, and microbial resistance. This topic covers chromosome structure, chromatin, nucleoid organization, histones, plasmids, operons, introns/exons, replication origins, and regulatory elements. Key concepts include genome size, gene density, polycistronic versus monocistronic transcription, nucleosome packaging, topoisomerases, and mobile genetic elements that mediate horizontal gene transfer and antibiotic resistance. Grasping these differences helps explain how drugs like topoisomerase inhibitors and epigenetic modulators work. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which characteristic best distinguishes eukaryotic genomic organization from prokaryotic organization?

• Presence of a membrane-bound nucleus and chromatin with histones
• Single circular chromosome localized in nucleoid
• Genes organized in operons producing polycistronic mRNA
• Replication controlled by a single origin in all chromosomes

Correct Answer: Presence of a membrane-bound nucleus and chromatin with histones

Q2. In bacteria, the compact DNA region lacking a nuclear membrane is called the:

• Nucleolus
• Chromatin
• Nucleoid
• Chromosome territory

Correct Answer: Nucleoid

Q3. Which protein family is primarily responsible for nucleosome formation in eukaryotes?

• Topoisomerases
• Histones
• HU proteins
• Sigma factors

Correct Answer: Histones

Q4. Polycistronic mRNA is a typical feature of which genetic organization?

• Eukaryotic nuclear transcription
• Prokaryotic operons
• Human mitochondrial genome
• Plant chloroplast transcription only

Correct Answer: Prokaryotic operons

Q5. Which element is essential for initiation of bacterial chromosomal replication?

• Telomere
• Origin of replication (OriC)
• TATA box
• Centromere

Correct Answer: Origin of replication (OriC)

Q6. Eukaryotic pre-mRNA processing events include all EXCEPT:

• 5′ capping
• Splicing of introns
• Polycistronic mRNA formation
• 3′ polyadenylation

Correct Answer: Polycistronic mRNA formation

Q7. Plasmids often carry genes relevant to pharmacy, such as:

• Ribosomal RNA genes required for translation
• Antibiotic resistance genes and virulence factors
• Telomerase genes for chromosome stability
• Centromeric binding factors

Correct Answer: Antibiotic resistance genes and virulence factors

Q8. Which bacterial proteins assist in DNA bending and compaction in the nucleoid?

• Histone H1 only
• Nucleoid-associated proteins like HU, IHF, and Fis
• RNA polymerase sigma factors
• Spliceosomal proteins

Correct Answer: Nucleoid-associated proteins like HU, IHF, and Fis

Q9. Which statement about introns and exons is correct?

• Introns are coding regions retained in mRNA
• Exons are noncoding regions removed during splicing
• Eukaryotic genes often contain introns that are spliced out to form mature mRNA
• Prokaryotic genes commonly contain many introns

Correct Answer: Eukaryotic genes often contain introns that are spliced out to form mature mRNA

Q10. Topoisomerase inhibitors used as drugs target which feature of genetic organization?

• Histone acetylation sites
• DNA supercoiling and replication machinery
• Ribosomal RNA operons
• Promoter methylation

Correct Answer: DNA supercoiling and replication machinery

Q11. The bacterial rho protein is involved in which process?

• DNA replication initiation
• Rho-dependent transcription termination
• Spliceosome assembly
• Telomere replication

Correct Answer: Rho-dependent transcription termination

Q12. Which feature is typical of eukaryotic chromosomes but not prokaryotic chromosomes?

• Circular DNA molecule
• Presence of telomeres and centromeres
• Operon structures
• Single origin per chromosome in bacteria

Correct Answer: Presence of telomeres and centromeres

Q13. The lac operon is best described as an example of:

• Constitutive gene expression without regulation
• Inducible operon regulated by lactose availability
• Operon controlling DNA replication
• Operon only found in eukaryotes

Correct Answer: Inducible operon regulated by lactose availability

Q14. What distinguishes euchromatin from heterochromatin in eukaryotes?

• Euchromatin is densely packed and transcriptionally inactive
• Heterochromatin is loosely packed and highly transcribed
• Euchromatin is loosely packed and transcriptionally active, while heterochromatin is condensed and silent
• Only heterochromatin contains histones

Correct Answer: Euchromatin is loosely packed and transcriptionally active, while heterochromatin is condensed and silent

Q15. Rolling-circle replication is commonly associated with which genetic element?

• Linear eukaryotic chromosomes
• Certain plasmids and some bacteriophages
• Mitochondrial genomes of mammals
• Ribosomal RNA gene clusters

Correct Answer: Certain plasmids and some bacteriophages

Q16. Which enzyme relieves supercoiling ahead of a replication fork in bacteria?

• DNA ligase
• DNA gyrase (a type II topoisomerase)
• RNA polymerase
• DNA helicase only

Correct Answer: DNA gyrase (a type II topoisomerase)

Q17. CRISPR loci in prokaryotes function primarily as:

• Replication origins
• Adaptive immune systems providing sequence-specific defense against phages
• Sites of ribosomal assembly
• Promoters for operon expression

Correct Answer: Adaptive immune systems providing sequence-specific defense against phages

Q18. Which statement about mitochondrial genomes is correct?

• Mitochondrial genomes are always linear and large like nuclear chromosomes
• Mitochondrial genomes are circular in many organisms and encode a subset of genes for respiration
• Mitochondria lack their own DNA entirely in eukaryotes
• Mitochondrial DNA is packaged into nucleosomes with histones

Correct Answer: Mitochondrial genomes are circular in many organisms and encode a subset of genes for respiration

Q19. Gene density (genes per Mb) is generally higher in which genomes?

• Eukaryotic nuclear genomes
• Prokaryotic genomes
• Human genome compared to bacterial genomes
• Plant nuclear genomes exclusively

Correct Answer: Prokaryotic genomes

Q20. Which DNA sequence element binds transcription factors to regulate eukaryotic gene expression?

• Operator sequence of bacterial operons
• Enhancers and promoters including TATA box
• OriC
• Rho utilization site

Correct Answer: Enhancers and promoters including TATA box

Q21. Which mechanism contributes to horizontal gene transfer among bacteria?

• Meiotic recombination
• Conjugation, transformation, and transduction
• Spliceosome-mediated trans-splicing
• Telomere shortening

Correct Answer: Conjugation, transformation, and transduction

Q22. A high GC content in a bacterial genome often correlates with:

• Lower DNA melting temperature
• Greater stability and higher melting temperature of DNA
• Absence of coding sequences
• Presence of introns similar to eukaryotes

Correct Answer: Greater stability and higher melting temperature of DNA

Q23. Histone acetylation generally leads to which chromatin state and effect on transcription?

• Condensed chromatin and transcriptional repression
• Relaxed chromatin and transcriptional activation
• No change in chromatin structure
• Permanent DNA methylation

Correct Answer: Relaxed chromatin and transcriptional activation

Q24. In prokaryotic transcription, the sigma factor is important for:

• DNA replication fork progression
• Recognizing promoter sequences and initiating transcription
• Splice site recognition
• Polyadenylation of mRNA

Correct Answer: Recognizing promoter sequences and initiating transcription

Q25. Transposons influence genomic organization by:

• Only removing nonfunctional DNA sequences permanently
• Moving within genomes and causing insertions, deletions, and rearrangements
• Facilitating splicing of introns
• Acting exclusively as origins of replication

Correct Answer: Moving within genomes and causing insertions, deletions, and rearrangements

Q26. Which feature allows plasmids to persist in bacterial populations at different copy numbers?

• Presence of telomeres
• Plasmid-specific replication origins and copy number control systems
• Packaging into nucleosomes
• Integration into eukaryotic chromosomes only

Correct Answer: Plasmid-specific replication origins and copy number control systems

Q27. Centromeres are functionally important for:

• Initiation of transcription
• Proper segregation of chromosomes during mitosis and meiosis
• RNA splicing accuracy
• Forming the nucleoid in bacteria

Correct Answer: Proper segregation of chromosomes during mitosis and meiosis

Q28. Which RNA is commonly transcribed as a polycistronic transcript in bacteria?

• mRNA from an operon encoding metabolic enzymes
• Eukaryotic pre-mRNA requiring splicing
• Individual monocistronic tRNAs only
• Mitochondrial rRNA exclusively

Correct Answer: mRNA from an operon encoding metabolic enzymes

Q29. DNA methylation in eukaryotes commonly affects gene expression by:

• Enhancing transcription at promoters
• Repressing transcription and contributing to heterochromatin formation
• Directly breaking DNA strands
• Preventing replication origin firing

Correct Answer: Repressing transcription and contributing to heterochromatin formation

Q30. Which genetic feature is a common target for antibacterial drugs to prevent DNA replication?

• Eukaryotic histone acetyltransferases
• Bacterial DNA gyrase and topoisomerase IV
• Mitochondrial ribosomes only found in eukaryotes
• Centromeric proteins of human chromosomes

Correct Answer: Bacterial DNA gyrase and topoisomerase IV

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com