TRB PG Assistant - DNA and RNA structure, replication, repair, transcription, RNA processing, genetic code Online Test (MCQ Quiz)

1. Which of the following is a key structural difference between DNA and RNA?

A) DNA contains deoxyribose sugar, while RNA contains ribose sugar. B) DNA is typically double-stranded, while RNA is typically single-stranded. C) DNA uses thymine as a base, while RNA uses uracil. D) All of the above.

2. In DNA, which base pairs with Adenine?

A) Guanine B) Cytosine C) Thymine D) Uracil

3. The DNA double helix is held together by which type of bonds?

A) Covalent bonds B) Phosphodiester bonds C) Hydrogen bonds D) Ionic bonds

4. What is the primary function of DNA?

A) Protein synthesis B) Carrying genetic information C) Catalyzing biochemical reactions D) Energy storage

5. Which enzyme is responsible for synthesizing new DNA strands during replication?

A) RNA polymerase B) DNA ligase C) Helicase D) DNA polymerase

6. The process by which DNA makes a copy of itself is called:

A) Transcription B) Translation C) Replication D) Mutation

7. During DNA replication, the lagging strand is synthesized:

A) Continuously in the 5' to 3' direction. B) Discontinuously in Okazaki fragments. C) In the 3' to 5' direction. D) By RNA polymerase.

8. What is the role of helicase in DNA replication?

A) To seal nicks in the DNA backbone. B) To unwind the DNA double helix. C) To synthesize RNA primers. D) To proofread the newly synthesized DNA.

9. Okazaki fragments are short segments of DNA synthesized on:

A) The leading strand. B) The lagging strand. C) Both leading and lagging strands. D) The template strand.

10. DNA repair mechanisms are crucial for:

A) Increasing mutation rates. B) Maintaining genomic stability. C) Initiating transcription. D) Producing new proteins.

11. Which type of DNA repair mechanism corrects errors made by DNA polymerase during replication?

A) Base excision repair B) Nucleotide excision repair C) Mismatch repair D) Photoreactivation repair

12. Nucleotide excision repair is a mechanism that removes and replaces damaged nucleotides caused by:

A) Mismatched bases. B) Single-strand breaks. C) Bulky lesions like UV-induced pyrimidine dimers. D) Deamination of bases.

13. The process of synthesizing RNA from a DNA template is called:

A) Replication B) Translation C) Reverse transcription D) Transcription

14. Which enzyme catalyzes transcription?

A) DNA polymerase B) RNA polymerase C) Reverse transcriptase D) Topoisomerase

15. In transcription, the DNA template strand sequence is read in which direction?

A) 5' to 3' B) 3' to 5' C) Both 5' to 3' and 3' to 5' D) Randomly

16. The RNA molecule synthesized during transcription has a sequence that is complementary to the template strand and similar to the:

A) Coding strand of DNA. B) Antisense strand of DNA. C) Non-coding strand of DNA. D) Regulatory region of DNA.

17. Which of the following is NOT a type of RNA involved in protein synthesis?

A) Messenger RNA (mRNA) B) Transfer RNA (tRNA) C) Ribosomal RNA (rRNA) D) Small nuclear RNA (snRNA)

18. What is the function of mRNA?

A) Carries amino acids to the ribosome. B) Forms the structural and catalytic core of ribosomes. C) Carries genetic information from DNA to the ribosome. D) Participates in RNA splicing.

19. What is the function of tRNA?

A) Carries genetic information from DNA to the ribosome. B) Forms the structural and catalytic core of ribosomes. C) Carries specific amino acids to the ribosome. D) Regulates gene expression.

20. What is the function of rRNA?

A) Carries amino acids to the ribosome. B) Forms the structural and catalytic core of ribosomes. C) Carries the genetic code from DNA. D) Modifies mRNA after transcription.

21. RNA processing in eukaryotes involves several steps, including:

A) Addition of a poly-A tail. B) Removal of introns (splicing). C) Addition of a 5' cap. D) All of the above.

22. What is the purpose of the 5' cap added to eukaryotic mRNA?

A) To facilitate ribosome binding for translation. B) To protect the mRNA from degradation. C) To signal the termination of transcription. D) To increase mRNA stability.

23. The process of removing non-coding regions (introns) from pre-mRNA and joining the coding regions (exons) is called:

A) Capping B) Polyadenylation C) Splicing D) Translation

24. Exons are:

A) Regions of DNA that are transcribed but not translated. B) Regions of pre-mRNA that are removed during splicing. C) Regions of mRNA that are translated into protein. D) Regions of DNA that regulate gene expression.

25. Introns are:

A) Regions of mRNA that are translated into protein. B) Regions of pre-mRNA that are removed during splicing. C) Regions of DNA that code for proteins. D) Regions that bind transcription factors.

26. The genetic code is a set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into:

A) Lipids B) Carbohydrates C) Proteins D) Nucleic acids

27. How many nucleotide bases form a codon?

A) One B) Two C) Three D) Four

28. The genetic code is described as degenerate because:

A) Some codons do not specify any amino acid. B) More than one codon can specify the same amino acid. C) The code changes over time. D) The code is different in different organisms.

29. Which of the following codons is a 'start' codon, initiating translation?

A) UAA B) UAG C) UGA D) AUG

30. Which of the following codons is a 'stop' codon, terminating translation?

A) AUG B) CGA C) UAG D) GGU

31. The genetic code is nearly universal, meaning:

A) It is identical in all living organisms. B) Most organisms use the same codons for the same amino acids. C) It only applies to prokaryotes. D) It has evolved independently multiple times.

32. What is the sequence of events in gene expression?

A) Replication -> Transcription -> Translation B) Transcription -> Replication -> Translation C) Transcription -> Translation -> Replication D) Translation -> Transcription -> Replication

33. Which of the following best describes the structure of RNA?

A) Double-stranded helix with deoxyribose sugar and thymine. B) Single-stranded helix with ribose sugar and uracil. C) Double-stranded helix with ribose sugar and uracil. D) Single-stranded helix with deoxyribose sugar and thymine.

34. Telomeres are repetitive DNA sequences at the ends of chromosomes that protect them from degradation. Their replication is a specialized process involving:

A) DNA polymerase only B) Reverse transcriptase and a special RNA template C) Primase and ligase D) Topoisomerase and helicase

35. A frameshift mutation occurs when there is an insertion or deletion of nucleotides that is:

A) A multiple of three. B) Not a multiple of three. C) A single nucleotide. D) A substitution.

36. Which enzyme is responsible for proofreading and removing incorrect nucleotides during DNA replication?

A) Telomerase B) Ligase C) Exonuclease activity of DNA polymerase D) Helicase

37. The process of transcription initiation in eukaryotes involves the binding of transcription factors to the:

A) Terminator sequence B) Promoter region C) Coding sequence D) Poly-A signal

38. Alternative splicing allows a single gene to produce multiple protein variants by:

A) Altering the DNA sequence. B) Modifying the promoter region. C) Including or excluding different exons from the final mRNA. D) Changing the start and stop codons.

39. Antisense RNA molecules can regulate gene expression by:

A) Binding to mRNA and preventing translation. B) Binding to DNA and blocking transcription. C) Catalyzing protein synthesis. D) Carrying amino acids to the ribosome.

40. The anticodon on a tRNA molecule is complementary to the:

A) Amino acid it carries. B) Ribosome binding site. C) Codon on the mRNA. D) Promoter region of DNA.

41. Which type of RNA interference mechanism uses short, double-stranded RNA molecules to trigger degradation of target mRNA?

A) siRNA (small interfering RNA) B) miRNA (microRNA) C) lncRNA (long non-coding RNA) D) piRNA (Piwi-interacting RNA)

42. The process of DNA repair that corrects damage from alkylating agents or ionizing radiation, often involving removal of a modified base and subsequent gap filling, is known as:

A) Mismatch repair B) Nucleotide excision repair C) Base excision repair D) Photoreactivation repair

43. In prokaryotes, transcription and translation can occur simultaneously because:

A) There is no nuclear envelope separating DNA and ribosomes. B) They lack introns. C) They have specialized RNA polymerases. D) Their ribosomes are smaller.

44. The Shine-Dalgarno sequence in prokaryotic mRNA is important for:

A) Initiating transcription. B) Terminating transcription. C) Initiating translation by binding to the ribosome. D) Splicing out introns.

45. What is the role of aminoacyl-tRNA synthetases?

A) To synthesize tRNA molecules. B) To attach the correct amino acid to its corresponding tRNA molecule. C) To bind mRNA to the ribosome. D) To form peptide bonds between amino acids.

46. Which of the following is a characteristic of the genetic code?

A) Non-overlapping B) Ambiguous C) Comprised of di-nucleotides D) Different in prokaryotes and eukaryotes

47. The process of reverse transcription, carried out by reverse transcriptase, synthesizes:

A) DNA from an RNA template. B) RNA from a DNA template. C) Protein from an RNA template. D) DNA from a DNA template.

48. Which enzyme is primarily responsible for joining Okazaki fragments on the lagging strand during DNA replication?

A) Helicase B) Primase C) DNA ligase D) Topoisomerase

49. A nucleoside differs from a nucleotide in that the nucleoside:

A) Lacks a phosphate group. B) Lacks a nitrogenous base. C) Lacks a pentose sugar. D) Is always purine-based.

50. The central dogma of molecular biology describes the flow of genetic information as:

A) Protein -> RNA -> DNA B) RNA -> DNA -> Protein C) DNA -> RNA -> Protein D) DNA -> Protein -> RNA

DNA and RNA structure, replication, repair, transcription, RNA processing, genetic code - Online Test

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