DNA is the fundamental molecule of heredity, and DNA Structure and Function MCQs for Class 12 Biology help aspirants understand this essential topic in a simple and exam-focused way. In Class 12 Biology, molecular genetics forms a major part of the syllabus, making DNA Structure and Function MCQs for Class 12 Biology extremely important for board examinations as well as NEET preparation. Aspirants who regularly practice DNA Structure and Function MCQs for Class 12 Biology gain better conceptual clarity about the organization, replication, and role of DNA in living organisms.

The study of DNA became more advanced after Watson and Crick proposed the double helix model, and today DNA Structure and Function MCQs for Class 12 Biology are among the most commonly asked questions in biology examinations. By solving DNA Structure and Function MCQs for Class 12 Biology, aspirants learn about nucleotide composition, complementary base pairing, antiparallel strands, and hydrogen bonding. These concepts are foundational for understanding heredity and genetic variation.

One major benefit of revising DNA Structure and Function MCQs for Class 12 Biology is that aspirants become comfortable with the terminology associated with molecular biology. Terms such as nucleosome, nucleotide, chromatin, gene expression, replication fork, and semiconservative replication are frequently included in DNA Structure and Function MCQs for Class 12 Biology. Continuous practice helps aspirants remember these terms more effectively and apply them accurately in examinations.

Another important reason why DNA Structure and Function MCQs for Class 12 Biology are useful is that they improve analytical and logical thinking. Many questions involve calculations related to base pairing or understanding the relationship between DNA structure and function. By solving DNA Structure and Function MCQs for Class 12 Biology, aspirants strengthen their ability to analyze biological data and solve conceptual problems quickly.

The concepts covered in DNA Structure and Function MCQs for Class 12 Biology are also essential for understanding advanced genetics and biotechnology. DNA is responsible for storing and transmitting hereditary information from one generation to another. Through regular practice of DNA Structure and Function MCQs for Class 12 Biology, aspirants learn how genetic information is replicated and expressed within cells. This forms the basis for understanding protein synthesis and inheritance.

One of the most important aspects explained through DNA Structure and Function MCQs for Class 12 Biology is the role of complementary base pairing. Adenine pairs with thymine, while guanine pairs with cytosine. These specific pairings maintain the stability of the DNA molecule. Aspirants who revise DNA Structure and Function MCQs for Class 12 Biology frequently develop a strong understanding of how DNA replication occurs accurately during cell division.

Another major advantage of practicing DNA Structure and Function MCQs for Class 12 Biology is that it strengthens NCERT-based preparation. Most biology entrance examinations directly ask conceptual questions related to DNA structure, replication, transcription, and genetic coding. Aspirants who solve DNA Structure and Function MCQs for Class 12 Biology consistently improve their confidence and exam performance significantly.

The importance of DNA Structure and Function MCQs for Class 12 Biology also extends to understanding modern biotechnology techniques such as DNA fingerprinting, PCR, recombinant DNA technology, and gene sequencing. These technologies rely heavily on the structural and functional properties of DNA. Through regular revision of DNA Structure and Function MCQs for Class 12 Biology, aspirants gain a stronger foundation for these advanced concepts.

In addition, DNA Structure and Function MCQs for Class 12 Biology help aspirants understand the relationship between genes and proteins. Genes are segments of DNA that carry instructions for protein synthesis. By practicing DNA Structure and Function MCQs for Class 12 Biology, aspirants learn how mutations in DNA can affect protein production and lead to genetic disorders. This improves both conceptual understanding and scientific reasoning.

Aspirants preparing for NEET especially benefit from DNA Structure and Function MCQs for Class 12 Biology because molecular genetics questions are frequently included in competitive examinations. Continuous practice of DNA Structure and Function MCQs for Class 12 Biology enhances speed, accuracy, and conceptual clarity. It also helps aspirants become more familiar with assertion-reason and application-based questions.

30 DNA Structure and Function MCQs for Class 12 Biology:

1. c-DNA is formed from m-RNA by which enzyme?
A. restriction endonuclease
B. reverse transcriptase
C. DNA polymerase
D. RNA polymerase

Answer: B. reverse transcriptase

Explanation: c-DNA is formed from m-RNA by the enzyme reverse transcriptase.

2. A typical nucleosome contains
A. 100 bp of DNA helix
B. 200 bp of DNA helix
C. 300 bp of DNA helix
D. 400 bp of DNA helix

Answer: B. 200 bp of DNA helix

Explanation: A typical nucleosome contains about 200 bp of DNA helix.

3. The small segment of DNA which helps to detect the presence of a gene or a long DNA sequence in biological system is termed as
A. DNA walker
B. cDNA
C. DNA clone
D. DNA probe

Answer: D. DNA probe

Explanation: A DNA probe helps detect the presence of a specific gene or DNA sequence.

4. In DNA when AGCT occurs, their association is as per which of the following pair?
A. AC – GT
B. AG – CT
C. AT – GC
D. All of these

Answer: C. AT – GC

Explanation: Adenine pairs with thymine and guanine pairs with cytosine.

5. What is a nucleosome?
A. DNA wrapped around histone protein
B. RNA wrapped around histone protein
C. Polymer
D. None of the above

Answer: A. DNA wrapped around histone protein

Explanation: A nucleosome is the basic structural unit of chromatin formed by DNA wrapped around histones.

6. The number of hydrogen bonds between adenine and thymine in a DNA molecule is:
A. two
B. three
C. four
D. eight

Answer: A. two

Explanation: Adenine and thymine are connected by two hydrogen bonds.

7. DNA element with the ability to change position is called:
A. cistron
B. transposon
C. intron
D. recon

Answer: B. transposon

Explanation: Transposons are mobile DNA sequences capable of changing position in the genome.

8. In a DNA molecule, the total quantity of purines is equal to the total quantity of pyrimidines. Adenine pairs with thymine and cytosine pairs with guanine. Mark the appropriate response:
A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
C. Assertion is true but Reason is false
D. Both Assertion and Reason are false

Answer: A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion

Explanation: Purines pair with pyrimidines according to Chargaff’s rule.

9. Nucleotide arrangement in DNA can be seen by:
A. X-ray crystallography
B. electron microscope
C. ultracentrifuge
D. light microscope

Answer: A. X-ray crystallography

Explanation: X-ray crystallography helped determine the DNA structure.

10. An analysis of a DNA (double-stranded) sample yielded 18% cytosine. What would be the percentage of other bases in this sample?
A. T–32
B. G–32
C. T–18
D. A–18

Answer: A. T–32

Explanation: If cytosine is 18%, guanine is also 18%, leaving 64% for adenine and thymine equally.

11. The modern concept of a gene is:
A. a segment of DNA, capable of crossing over
B. functional unit of DNA
C. a segment of RNA
D. a segment of chromosome

Answer: B. functional unit of DNA

Explanation: Genes are functional units of heredity made of DNA.

12. Locations on sites in the human DNA where single base DNA differences occur are called
A. Repetitive DNA
B. VNTR
C. SNP
D. Expressed sequence tags

Answer: C. SNP

Explanation: SNP stands for Single Nucleotide Polymorphism.

13. The bonds that hold the two complementary strands of DNA together are
A. Ionic bonds
B. Peptide bonds
C. Phosphodiester bonds
D. Hydrogen bonds

Answer: D. Hydrogen bonds

Explanation: Hydrogen bonds connect complementary nitrogen bases.

14. The complementary synthetic and random DNA are used as
A. transposons
B. passenger DNA
C. cloning vectors
D. recombinant DNA

Answer: B. passenger DNA

Explanation: Passenger DNA refers to foreign DNA inserted into vectors.

15. DNA can be 1.A-DNA 2.B-DNA 3.Z-DNA 4.Y-DNA
A. 1, 2 and 3 are correct
B. 1 and 2 are correct
C. 2 and 4 are correct
D. 1 and 3 are correct

Answer: A. 1, 2 and 3 are correct

Explanation: A-DNA, B-DNA, and Z-DNA are known forms of DNA.

16. McClintock is related to
A. plasmids
B. retroposons
C. transposons
D. none of these

Answer: C. transposons

Explanation: Barbara McClintock discovered transposons in maize.

17. Crick, one of the discoverers of DNA double helical structure, was a man of
A. Physics
B. Chemistry
C. Zoology
D. Botany

Answer: A. Physics

Explanation: Francis Crick had a background in physics.

18. Nitrogen base + Pentose sugar + Phosphate group is
A. nucleoside
B. nucleotide
C. nucleic acid
D. pyrimidine base

Answer: B. nucleotide

Explanation: A nucleotide consists of base, sugar, and phosphate.

19. DNA is present in
A. nucleus only
B. mitochondrion only
C. chloroplast only
D. All of these

Answer: D. All of these

Explanation: DNA occurs in nucleus, mitochondria, and chloroplasts.

20. In a DNA molecule, at the 5′ end there is a free _____
A. oxygen
B. nitrogen
C. phosphate
D. hydroxyl

Answer: C. phosphate

Explanation: The 5′ end of DNA contains a free phosphate group.

21. When DNA is formed from RNA, it is called
A. D-DNA
B. Z-DNA
C. C-DNA
D. A-DNA

Answer: C. C-DNA

Explanation: DNA synthesized from RNA is referred to as cDNA.

22. The anti-parallel nature of DNA refers to
A. its charged phosphate groups
B. the formation of hydrogen bonds between bases from opposite strands
C. the opposite direction of the two strands
D. the pairing of bases on one strand with bases on the other strand

Answer: C. the opposite direction of the two strands

Explanation: DNA strands run in opposite directions.

23. Beadle and Tatum showed that each kind of mutant bread mould they studied lacked a specific enzyme. Their experiments demonstrated that
A. cells need specific enzymes in order to function
B. genes are made of DNA
C. enzymes are required to repair damage
D. genes carry information for making proteins

Answer: D. genes carry information for making proteins

Explanation: Their work supported the one gene-one enzyme hypothesis.

24. In DNA helix cytosine paired with guanine by :
A. covalent bond
B. phosphate bond
C. two H₂ bonds
D. three H₂ bonds

Answer: D. three H₂ bonds

Explanation: Cytosine and guanine are linked by three hydrogen bonds.

25. DNA is acidic due to
A. sugar
B. phosphoric acid
C. purine
D. pyrimidine

Answer: B. phosphoric acid

Explanation: Phosphate groups make DNA acidic.

26. Stain used by Feulgen to stain DNA is
A. janus green
B. basic fuschin
C. crystal violet
D. methylene blue

Answer: B. basic fuschin

Explanation: Feulgen stain uses basic fuschin for DNA visualization.

27. A, B, and C are the three forms of DNA, in which
A. A and B are right-handed and C is left-handed
B. A is right-handed and B and C are left-handed
C. All three are right-handed, but the number of bases per turn differs
D. All three are left-handed, but the number of base pairs per turn differs

Answer: C. All three are right-handed, but the number of bases per turn differs

Explanation: A-DNA, B-DNA, and C-DNA differ in structural parameters.

28. Which is the unit of DNA?
A. Chromatin
B. Euchromatin
C. Chromosomes
D. Chromatids

Answer: A. Chromatin

Explanation: Chromatin is the DNA-protein complex forming chromosomes.

29. How many nucleosomes are found in helical coil of 30 nm chromatin fibre?
A. 6
B. 10
C. 12
D. 9

Answer: A. 6

Explanation: Approximately 6 nucleosomes form one turn of the 30 nm chromatin fibre.

30. The barr body is observed in
A. 3% male basophils
B. 3% female basophils
C. 3% male neutrophils
D. 3% female neutrophils

Answer: D. 3% female neutrophils

Explanation: Barr bodies are seen in some female neutrophils.

In conclusion, DNA Structure and Function MCQs for Class 12 Biology are extremely important for mastering molecular genetics and heredity. Regular practice of DNA Structure and Function MCQs for Class 12 Biology improves conceptual understanding, strengthens problem-solving skills, and increases examination confidence. Whether preparing for school exams or medical entrance tests, aspirants should revise DNA Structure and Function MCQs for Class 12 Biology regularly to build a strong foundation in biology.