DNA Structure Quiz - CBSE Class 12 Biology

Free practice quiz: DNA Structure (CBSE Class 12 Biology). 19 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This CBSE Class 12 Biology practice quiz has 19 multiple-choice questions on DNA Structure, and 19 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. What is the basic building block of DNA?

   1. Amino acid
   2. Nucleotide
   3. Fatty acid
   4. Simple sugar
   Show answer

   Answer: B. Nucleotide

   The basic building block of DNA is the nucleotide, which consists of a sugar, a phosphate group, and a nitrogenous base.

2. Which nitrogenous base pairs with adenine in DNA?

   1. Thymine
   2. Cytosine
   3. Guanine
   4. Uracil
   Show answer

   Answer: A. Thymine

   In DNA, adenine pairs with thymine via two hydrogen bonds, forming base pairs.

3. Which enzyme is responsible for unwinding DNA during replication?

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

   Answer: B. Helicase

   Helicase is the enzyme responsible for unwinding the DNA double helix during replication.

4. How many base pairs are in a complete turn of the DNA double helix?

   1. 10
   2. 12
   3. 15
   4. 20
   Show answer

   Answer: A. 10

   In a complete turn of the DNA double helix, there are approximately 10 base pairs.

5. What is the function of telomeres in DNA?

   1. To replicate DNA
   2. To protect chromosome ends
   3. To produce RNA
   4. To join nucleotide strands
   Show answer

   Answer: B. To protect chromosome ends

   Telomeres are repetitive sequences at the ends of chromosomes that protect them from degradation.

More questions in this quiz

Answers and explanations are in the full quiz.

1. Which part of the nucleotide varies among different nucleotides?
2. What type of bond holds the two strands of DNA together?
3. What is the primary structure of DNA described as?
4. In what direction is DNA synthesized?
5. What type of DNA is found in prokaryotes?
6. Which nitrogenous base is not found in DNA?
7. What is the function of DNA ligase?
8. What is the role of the sugar-phosphate backbone in DNA?
9. Which type of RNA is involved in the process of translating DNA into protein?
10. What is meant by DNA replication being semi-conservative?
11. Which feature of DNA allows it to encode genetic information?
12. How do mutations affect DNA structure?
13. What mechanism does DNA use to repair itself?
14. Which scientist(s) is/are credited with the discovery of the DNA double helix structure?

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