MCQ on DNA Pdf

• Nucleic acid is a biological macromolecular compound composed of many nucleotides and is one of the most basic substances of life.
• There are two types of nucleic acid DNA and RNA.
• DNA is the carrier of all genetic information. 
• DNA is a macromolecular polymer composed of deoxynucleotides.
• Deoxynucleotides are composed of bases, deoxyribose sugars, and phosphates.
• There are four bases: adenine (A), guanine (G), thymine (T), and cytosine (C).
• The diameter of the helix is ​​2 nm; the helix period contains 10 pairs of bases; the pitch of the helix is ​​3.4 nm; the distance between the planes of adjacent base pairs is 0.34 nm.
• The DNA molecule is a double helix structure formed by two anti-parallel long chains of deoxynucleotides.
• The deoxyribose and phosphate in the DNA molecule are alternately connected and arranged on the outside to form the basic skeleton; the bases are arranged on the inside.
• Base pairings are always A with T and G with C. Base pairs are held together by hydrogen bonds, two hydrogen bonds are formed between A and T, and three hydrogen bonds are formed between G and C. 
• DNA carries The genetic information necessary for the synthesis of RNA and proteins is essential for the development and normal functioning of organisms.”

MCQ on DNA with Answers Pdf

1. Who discovered DNA?
(A) Friedrich Miescher
(B) James Watson
(C) Francis Crick
(D) Altman
Answer: (A) Friedrich Miescher
Explanation: He discovered a substance from white blood cells in 1869 and named it “nuclein,” now known as DNA.

2. The basic unit of DNA molecule is
(A) Deoxyribonucleotides
(B) Ribonucleotides
(C) Nitrogenous bases
(D) Gene
Answer: (A) Deoxyribonucleotides
Explanation: DNA is composed of deoxyribonucleotides—each made of a sugar, phosphate, and nitrogenous base.

3. The double helix structure of DNA was discovered by
(A) Friedrich Miescher
(B) James Watson
(C) Francis Crick
(D) Both (B) and (C)
Answer: (D) Both (B) and (C)
Explanation: James Watson and Francis Crick discovered the double-helix structure of DNA in 1953.

4. Which is the monomer of DNA?
(A) Deoxyribonucleotides
(B) Ribonucleotides
(C) Nitrogenous bases
(D) Gene
Answer: (A) Deoxyribonucleotides
Explanation: DNA is made up of repeating units called deoxyribonucleotides.

5. What is the full form of DNA?
(A) Degenerative acid
(B) Deoxyribonucleic acid
(C) Deadly nucleic acid
(D) Disoriented acid
Answer: (B) Deoxyribonucleic acid
Explanation: DNA stands for Deoxyribonucleic Acid.

6. What is the most common form of DNA?
(A) B-form
(B) Z-form
(C) B-form
(D) None of these
Answer: (A) B-form
Explanation: B-form DNA is the most common and biologically significant form under normal conditions.

7. Compared to RNA, the unique components of DNA are
(A) Ribose and uracil
(B) Deoxyribose and thymine
(C) Deoxyribose and uracil
(D) Deoxyribose and guanine
Answer: (B) Deoxyribose and thymine
Explanation: DNA has deoxyribose sugar and thymine instead of ribose and uracil in RNA.

8. The following substances that can polymerize to form DNA molecules are
(A) Deoxyribose
(B) Deoxynucleotides
(C) Amino acid
(D) Nitrogenous base
Answer: (B) Deoxynucleotides
Explanation: Deoxynucleotides are the monomers that polymerize to form DNA chains.

9. What is the backbone of DNA?
(A) Phosphate backbone
(B) Sugar backbone
(C) Adenine backbone
(D) Both (B) and (C)
Answer: (A) Phosphate backbone
Explanation: The backbone of DNA is made of alternating deoxyribose sugar and phosphate groups.

10. DNA in human epithelial cells is present in
(A) Nucleus, chloroplasts, mitochondria
(B) Nucleus, mitochondria
(C) Nucleus
(D) Nucleus, ribosome, mitochondria
Answer: (B) Nucleus, mitochondria
Explanation: Human cells contain DNA in the nucleus and mitochondria, but not in chloroplasts or ribosomes.

11. What is the shape of DNA?
(A) Double helix
(B) Triple helix
(C) Both
(D) None of these
Answer: (A) Double helix
Explanation: DNA has a double-helical structure formed by two strands twisted around each other.

12. If the DNA strand has nitrogenous base sequence ATT GCC, the mRNA will have
(A) ATTGCA
(B) UGGACC
(C) UAACGG
(D) ATCGCC
Answer: (C) UAACGG
Explanation: The complementary mRNA sequence is formed by replacing A with U, T with A, and G with C.

13. DNA in wheat root tip is present in
(A) Nucleus, chloroplast, and Golgi
(B) Endoplasmic reticulum, mitochondria, and nucleus
(C) Mitochondria, chloroplasts, and nucleus
(D) Nucleus, mitochondria
Answer: (D) Nucleus, mitochondria
Explanation: DNA in plant cells is present in the nucleus, mitochondria, and chloroplasts, but Golgi does not contain DNA.

14. A group of the following structures all containing DNA is
(A) Chloroplast, Golgi, centrosome, chromosome
(B) Chloroplasts, mitochondria, nucleus, bacterial plasmids
(C) Endoplasmic reticulum, ribosome, nucleus, centrosome
(D) Mitochondria, ribosomes, chromosomes, Golgi apparatus
Answer: (B) Chloroplasts, mitochondria, nucleus, bacterial plasmids
Explanation: All these are known to contain DNA.

15. Which of the following is not a correct statement concerning DNA?
(A) It is a long polymer
(B) It is found in the nucleus
(C) It is a basic substance
(D) First identified by Friedrich Miescher
Answer: (C) It is a basic substance
Explanation: DNA is an acidic molecule due to its phosphate groups.

16. Which of the following is a component of DNA?
(A) Deoxyribose, nucleic acid, and phosphate
(B) Deoxyribose, base, and phosphate
(C) Ribose, base, and phosphate
(D) Nucleosides, bases, and phosphates
Answer: (B) Deoxyribose, base, and phosphate
Explanation: DNA nucleotides are composed of a sugar (deoxyribose), a phosphate, and a nitrogenous base.

17. The substance that can be obtained after complete hydrolysis of DNA is
(A) Amino acid
(B) Amino acids and deoxynucleotides
(C) Carbon dioxide, water, and N-containing wastes
(D) Deoxyribose, N-containing bases, and phosphates
Answer: (D) Deoxyribose, N-containing bases, and phosphates
Explanation: DNA breaks down into its component sugars, bases, and phosphate groups.

18. Which of the following statements about the basic functions of DNA is incorrect?
(A) Genetic information is stored in DNA
(B) DNA transfers genetic information through replication
(C) DNA is the embodiment of biological traits
(D) DNA expresses genetic information through transcription and translation
Answer: (C) DNA is the embodiment of biological traits
Explanation: DNA contains instructions for traits but is not the direct expression of them.

19. By which of the following bonds is a nitrogenous base linked to pentose sugar?
(A) Phosphate bond
(B) Ester bond
(C) Peptide bond
(D) N-glycosidic bond
Answer: (D) N-glycosidic bond
Explanation: Nitrogenous bases are linked to the sugar (deoxyribose) by N-glycosidic bonds.

20. Which of the following statements about DNA is false?
(A) DNA in the nucleus of various somatic cells of the same organism has the same base composition
(B) The base content of a double-stranded DNA molecule is A+G = C+T or A+C = G+T
(C) The base content of a double-stranded DNA molecule is A/T = G/C
(D) DNA is only found in the nucleus
Answer: (D) DNA is only found in the nucleus
Explanation: DNA is also found in mitochondria (and in chloroplasts in plants).

21. This force can stabilize a DNA double helix
(A) Hydrophilic sugar-phosphate groups on the exterior interact with water
(B) Hydrophobic bases are in the interior; each pair is stabilized by the same number of hydrogen bonds
(C) Covalent base stacking interactions between neighboring bases
(D) Non-covalent N-glycosidic bonds form between bases of opposite strands
Answer: (A) Hydrophilic sugar-phosphate groups on the exterior interact with water
Explanation: The hydrophilic exterior and hydrophobic interior stabilize the DNA structure.

22. In this type of DNA replication, of the two newly formed molecules, one is purely new and the other is old
(A) Dispersive
(B) Conservative
(C) Semiconservative
(D) Both (B) and (C)
Answer: (C) Semiconservative
Explanation: Semiconservative replication means each new DNA has one old and one new strand.