Molecular Basis of Inheritance – DNA Replication, Genetic Code, Gene Expression Quiz - ICSE Class 12 Biology

Free practice quiz: Molecular Basis of Inheritance – DNA Replication, Genetic Code, Gene Expression (ICSE Class 12 Biology). 39 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This ICSE Class 12 Biology practice quiz has 39 multiple-choice questions on Molecular Basis of Inheritance – DNA Replication, Genetic Code, Gene Expression, and 39 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. During DNA replication, the enzyme that catalyzes the formation of phosphodiester bonds between nucleotides is:

   1. Helicase
   2. DNA polymerase
   3. Ligase
   4. Topoisomerase
   Show answer

   Answer: B. DNA polymerase

   DNA polymerase is the primary enzyme responsible for synthesizing new DNA strands by adding nucleotides and forming phosphodiester bonds. Helicase unwinds the DNA, ligase seals nicks, and topoisomerase relieves supercoiling.

2. The term 'antiparallel' in the context of DNA structure refers to:

   1. The complementary base pairing between strands
   2. The sugar-phosphate backbone running in opposite directions
   3. The double helical structure
   4. The presence of two strands
   Show answer

   Answer: B. The sugar-phosphate backbone running in opposite directions

   Antiparallel means that the two strands of the DNA double helix are oriented in opposite directions with respect to their 5' and 3' ends. One strand runs 5' to 3', while the complementary strand runs 3' to 5'.

3. Which of the following DNA sequences would be recognized by a restriction enzyme that recognizes the palindromic sequence 5'-GAATTC-3'?

   1. 5'-CTTAAG-3'
   2. 5'-TTAAGC-3'
   3. 5'-AGCTAG-3'
   4. 5'-CATGCATG-3'
   Show answer

   Answer: A. 5'-CTTAAG-3'

   A palindromic sequence reads the same forwards on one strand as it does backwards on the complementary strand. The complementary strand to 5'-GAATTC-3' is 3'-CTTAAG-5'. When read in the 5' to 3' direction, the complementary strand is 5'-CTTAAG-3'. Therefore, the sequence 5'-CTTAAG-3' is the reverse complement of 5'-GAATTC-3', and a restriction enzyme recognizing GAATTC would also recognize CTTAAG on the opposite strand.

4. The promoter region in a gene:

   1. Is the site where transcription terminates.
   2. Is the site where the repressor protein binds.
   3. Is the site where RNA polymerase binds to initiate transcription.
   4. Codes for a structural protein.
   Show answer

   Answer: C. Is the site where RNA polymerase binds to initiate transcription.

   The promoter is a regulatory DNA sequence located upstream of the coding sequence of a gene. It serves as the binding site for RNA polymerase and other transcription factors, initiating the process of transcription.

5. The genetic code is redundant. This means:

   1. Most amino acids are specified by only one codon.
   2. All codons specify amino acids.
   3. Some amino acids are specified by more than one codon.
   4. The code is not universal.
   Show answer

   Answer: C. Some amino acids are specified by more than one codon.

   Redundancy or degeneracy of the genetic code signifies that a single amino acid can be encoded by multiple different codons. This is a key feature that helps to buffer against mutations.

More questions in this quiz

Answers and explanations are in the full quiz.

1. In prokaryotic gene expression, the operator region is typically located:
2. The process by which an mRNA molecule is synthesized from a DNA template is called:
3. If the template strand of a DNA molecule has the sequence 3'-TACGATGCA-5', what will be the sequence of the transcribed mRNA molecule?
4. The genetic code is read in triplets of bases called:
5. Which enzyme is responsible for unwinding the DNA double helix during replication?
6. A mutation that changes a single nucleotide base in a gene is called a:
7. Which of the following amino acids is encoded by the codon UUU?
8. In eukaryotes, transcription occurs in the _______, while translation occurs in the _______.
9. The enzyme responsible for adding RNA primers to initiate DNA synthesis is:
10. Consider a non-sense mutation. If a DNA sequence originally translates to 'Met-Arg-Gly-Ser', and a non-sense mutation occurs at the codon for Glycine, what would be the resulting polypeptide chain?
11. Which of the following molecules serves as a template for translation?
12. The anticodon loop of a tRNA molecule carries:
13. During DNA replication, the enzyme responsible for removing RNA primers and replacing them with DNA is:
14. The 'central dogma' of molecular biology describes the flow of genetic information as:
15. A frameshift mutation is caused by:
16. Which of the following helps in the separation of DNA strands during replication by preventing re-annealing?
17. The genetic code has 64 possible codons. How many of these are 'sense' codons that specify an amino acid?
18. In the lac operon, the gene product of the 'lac I' gene is:
19. DNA replication is said to be semi-conservative because:
20. Which of the following is an example of a degenerate genetic code?
21. During DNA replication, the enzyme DNA ligase is primarily responsible for:
22. Which type of mutation is least likely to affect protein function?
23. A mutation occurs in the operator region of the lac operon. If this mutation prevents the repressor protein from binding, what will be the consequence?
24. In DNA replication, the enzyme responsible for synthesizing the new DNA strands is called:
25. If the mRNA codon is 5'-GGC-3', what tRNA anticodon sequence will bind to it?
26. Eukaryotic DNA replication is considered more complex than prokaryotic replication due to:
27. If the DNA template strand is 3'-TTACCGGTA-5', the resulting mRNA sequence will be:
28. The process by which a bacterial operon can be turned OFF by the presence of a specific molecule is called:
29. If a DNA sequence contains a mutation that changes the codon UCU (Serine) to UCU (Serine), this is an example of:
30. The sigma factor in bacterial transcription is responsible for:
31. The template for DNA replication is:
32. The region of DNA that codes for a protein is called:
33. Which of the following statements about DNA replication is TRUE?
34. If the DNA sequence has a mutation that changes the codon CGA (Arginine) to UGA (Stop), what is the effect?

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