Multiple-Choice Questions with Answers on “The Nucleus: DNA Storage and Gene Regulation”

Section 1: Structure and Function of the Nucleus

1. Which of the following structures encloses the nucleus?
   a) Plasma membrane
   b) Nuclear envelope
   c) Cytoplasmic reticulum
   d) Golgi apparatus
   Answer: b) Nuclear envelope
2. What is the primary function of nuclear pores?
   a) DNA replication
   b) Ribosome synthesis
   c) Transport of molecules in and out of the nucleus
   d) Protein degradation
   Answer: c) Transport of molecules in and out of the nucleus
3. Which type of RNA is synthesized in the nucleus?
   a) tRNA
   b) mRNA
   c) rRNA
   d) All of the above
   Answer: d) All of the above
4. Where in the nucleus are ribosomal subunits assembled?
   a) Chromosome
   b) Nucleolus
   c) Nuclear pore
   d) Nuclear matrix
   Answer: b) Nucleolus
5. What structure organizes and compacts DNA within the nucleus?
   a) Microtubules
   b) Histones
   c) Ribosomes
   d) Peroxisomes
   Answer: b) Histones

Section 2: DNA and Chromatin

6. What is chromatin composed of?
   a) DNA and lipids
   b) RNA and proteins
   c) DNA and proteins
   d) DNA and carbohydrates
   Answer: c) DNA and proteins
7. Which type of chromatin is transcriptionally active?
   a) Euchromatin
   b) Heterochromatin
   c) Both a and b
   d) Neither a nor b
   Answer: a) Euchromatin
8. What is the repeating unit of chromatin?
   a) Nucleosome
   b) Centromere
   c) Telomere
   d) Chromatid
   Answer: a) Nucleosome
9. What is the function of telomeres?
   a) To regulate gene expression
   b) To protect the ends of chromosomes
   c) To assist in DNA replication
   d) To synthesize proteins
   Answer: b) To protect the ends of chromosomes
10. How many base pairs wrap around a nucleosome core particle?
    a) 100
    b) 146
    c) 200
    d) 256
    Answer: b) 146

Section 3: DNA Replication and Repair

11. DNA replication occurs during which phase of the cell cycle?
    a) G1 phase
    b) S phase
    c) G2 phase
    d) M phase
    Answer: b) S phase
12. Which enzyme unwinds DNA during replication?
    a) DNA polymerase
    b) Helicase
    c) Ligase
    d) Topoisomerase
    Answer: b) Helicase
13. Which enzyme is responsible for synthesizing new DNA strands?
    a) RNA polymerase
    b) DNA ligase
    c) DNA polymerase
    d) Primase
    Answer: c) DNA polymerase
14. What is the function of DNA ligase?
    a) To unwind DNA
    b) To join Okazaki fragments
    c) To remove RNA primers
    d) To initiate transcription
    Answer: b) To join Okazaki fragments
15. Which repair mechanism corrects mismatched base pairs?
    a) Base excision repair
    b) Mismatch repair
    c) Nucleotide excision repair
    d) Homologous recombination
    Answer: b) Mismatch repair

Section 4: Gene Regulation

16. Which molecule serves as the template for transcription?
    a) RNA
    b) DNA
    c) Protein
    d) Lipid
    Answer: b) DNA
17. Which enzyme synthesizes RNA during transcription?
    a) RNA polymerase
    b) DNA polymerase
    c) Reverse transcriptase
    d) Helicase
    Answer: a) RNA polymerase
18. What is the role of promoters in gene regulation?
    a) To terminate transcription
    b) To initiate transcription
    c) To replicate DNA
    d) To splice RNA
    Answer: b) To initiate transcription
19. What is the function of enhancers in gene regulation?
    a) They increase the efficiency of transcription.
    b) They terminate RNA synthesis.
    c) They synthesize proteins.
    d) They protect the DNA ends.
    Answer: a) They increase the efficiency of transcription.
20. Which proteins bind to DNA to regulate transcription?
    a) Helicases
    b) Transcription factors
    c) Ribosomal proteins
    d) Histones
    Answer: b) Transcription factors

Section 5: RNA Processing and Translation

21. What is the process of removing introns from RNA called?
    a) Splicing
    b) Transcription
    c) Translation
    d) Replication
    Answer: a) Splicing
22. What is added to the 5′ end of eukaryotic mRNA?
    a) Poly-A tail
    b) 5′ cap
    c) Ribosomal RNA
    d) Promoter
    Answer: b) 5′ cap
23. What is the role of a poly-A tail in mRNA?
    a) Protect mRNA from degradation
    b) Initiate transcription
    c) Facilitate intron splicing
    d) Bind to ribosomes
    Answer: a) Protect mRNA from degradation
24. Which codon signals the start of translation?
    a) UAA
    b) AUG
    c) UAG
    d) UGA
    Answer: b) AUG
25. What is the role of tRNA in translation?
    a) Synthesizing DNA
    b) Carrying amino acids to the ribosome
    c) Unwinding DNA
    d) Forming RNA
    Answer: b) Carrying amino acids to the ribosome

Section 6: Advanced Topics in Gene Regulation

26. Which mechanism allows a single gene to produce multiple proteins?
    a) Alternative splicing
    b) DNA methylation
    c) RNA polymerization
    d) Chromosome condensation
    Answer: a) Alternative splicing
27. What is the effect of DNA methylation on gene expression?
    a) Enhances expression
    b) Silences expression
    c) Replaces nucleotides
    d) Repairs damaged DNA
    Answer: b) Silences expression
28. What are operons typically found in?
    a) Eukaryotic cells
    b) Prokaryotic cells
    c) Viruses
    d) Mitochondria
    Answer: b) Prokaryotic cells
29. Which of the following is an example of a transcriptional repressor?
    a) Lac repressor
    b) RNA polymerase
    c) Ribosome
    d) Histone acetylase
    Answer: a) Lac repressor
30. Which protein complex degrades tagged proteins in eukaryotic cells?
    a) Proteasome
    b) Ribosome
    c) Lysosome
    d) Peroxisome
    Answer: a) Proteasome