NEET Biology The DNA Multiple Choice Question And Answers

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Biology MCQs with answers for NEET The DNA

Question 1. ………….. was the first to isolate nucleic acids.

  1. Miescher
  2. Altman
  3. Kornberg
  4. Mendel

Answer: 1. Miescher

Nucleic acid was first isolated in 1868 by Swiss physician Friedrich Miescher from the nuclei of pus cells and he called it nuclein.

It was later named nucleic acid by Altman in1889

Question 2. The name nucleic acid is derived from

  1. The type of sugar it contains
  2. Its abundance in nuclei
  3. Its hydrophilic or water-loving nature
  4. The type of phosphates it contains

Answer: 1. The type of sugar it contains

The name of nucleic acid is derived from the type of sugar it contains. There are two types of nucleic acids. DNA contains deoxyribose sugar whereas RNA contains ribose sugar

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Question 3. A nucleotide consists of

  1. Purine, pyrimidine and phosphate
  2. Purine, sugar, and phosphate
  3. Nitrogen base, sugar, and phosphate
  4. Pyrimidine, sugar, and phosphate

Answer: 3. nitrogen base, sugar, and phosphate

“questions about dna “

Nucleotide is a unit of DNA, which is formed of nitrogenous bases (purines and pyrimidines), sugar (pentose), and phosphate.

Biology MCQs with answers for NEET

NEET Biology The DNA Multiple Choice Question And Answers

Question 4. Watson and Crick are known for their discovery that DNA

  1. Is a single-stranded helix
  2. Contains deoxyribose only
  3. Is a double-stranded helix
  4. Synthesizes rRNA

Answer: 3. is a double-stranded helix

According to the Watson-Crick Model, a DNA molecule consists of two long parallel chains that are spirally coiled around a common axis in a regular manner to form a double helix.

Question 5. DNA is a

  1. Long Polymer Of Deoxyribonucleotides
  2. Short Polymer Of Deoxyribonucleotides
  3. Monomer Polymer Of Deoxyribonucleotides
  4. Long Polymer Of Ribonucleotides

Answer: 1. Long polymer of deoxyribonucleotides

DNA is a long chain of polymer of deoxyribonucleotide in which a phosphate group is attached to 5′- OH of nucleoside through phosphodiester linkage.

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Question 6. Consider the following statements.

  1. The double helix model of DNA resembles a twisted ladder.
  2. In the DNA helix, purine and pyrimidines are found.

Choose the correct option.

  1. Statement 1 is correct, but 2 is incorrect
  2. Statement 1 is incorrect, but 2 is correct
  3. Both statements 1 and 2 are correct
  4. Both statements 1 and 2 are incorrect

Answer: 3. Both statements 1 and 2 are correct.

Base pairs are complementary nitrogen bases present in two DNA strands, with a purine lying opposite to a pyrimidine or vice-versa. This purine-pyrimidine association is required for proper spatial arrangement and hydrogen bonding.

Hydrogen bonding, base stacking, and hydrophobic interactions between bases are the forces that help to keep the two DNA strands together.

Question 7. DNA is a genetic material due to

  1. Its stability.
  2. Its ability to replicate.
  3. Its ability to mutate.
  4. Its ability to express itself.

Choose the correct combination.

  1. 1 and 2
  2. 1, 3 and 4
  3. 3 and 4
  4. 1, 2, 3 and 4

Answer: 4. 1, 2, 3 and 4

DNA acts as genetic material as it shows the following properties The replicated DNA is transferred faithfully from cells to its daughter cells or from one generation to another. It is able to express itself.

It undergoes occasional changes or mutations in the structure and functioning of its genes, which are of permanent nature and inheritable. It is relatively a stable molecule.

It is the same in both quality and quantity in all cells of an individual. Thus, option 4 is correct.

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Question 8. Antiparallel strands of a DNA molecule mean that

  1. One strand turns clockwise
  2. One strand turns anti-clockwise
  3. The phosphate groups of two DNA strands, at their ends, share the same position
  4. The phosphate groups at the start of two DNA strands are in opposite positions (pole)

Answer: 4. the phosphate groups at the start of two DNA strands are in opposite positions (pole)

The two strands of DNA run in opposite directions to one another with hydrogen bonds between them. One strand of DNA has a 5′-3′ direction and the other strand has a 3′-5′ direction. So, they are antiparallel.

This direction is determined by the presence of a free phosphate or hydroxy (— OH) group at the end of the strand. The strand has a phosphate group at the 5′ end and a free OH group at the 3′ end.

Biology MCQs with answers for NEET

Question 9. In the double-helical structure of DNA, the pitch of the helix is Kerala

  1. 3.4 nm
  2. 0.34 nm
  3. 6.6 nm
  4. 34 nm
  5. 6.6 x 10−9 m

Answer: 1. 3.4 nm

In the commonly found double helical structure of B-DNA, one turn of the spiral has about 10 nucleotides. It occupies a distance (pitch) of about 3.4 nm (34Å)

Question 10. The distance between the two consecutive base pairs of DNA is

  1. 3.4 µm
  2. 3.4 Å
  3. 0.34 x 10−9 m
  4. Both (2) and (3)

Answer: 4. Both (2) and (3)

The distance between the two nucleotide base pairs of DNA is 3.4 Å or 0.34 nm or 0.34 × 10−9m. Thus, the option is correct.

Question 11. Each strand of DNA has

  1. 3′ end and 6′ end
  2. 5′ end and 5′ end
  3. 3′ end and 5′ end
  4. 3′ end and 3′ end

Answer: 3. 3′ end and 5′ end

Each strand has one free phosphate group on the 5th carbon of the sugar molecule.

This end of the strand is called the 5′ end. The other end of the strand has a free — OH group on the 3rd carbon of the sugar molecule.

This is called the 3′ end of the strand. So, each strand has 3′ end and 5′ end

Question 12. The diploid content of human DNA is

  1. 3.3 × 106 bp
  2. 33 × 109 bp
  3. 4.6 × 106 bp
  4. 6.6 × 109 bp

Answer: 4. 6.6 × 109 bp

The haploid content of human DNA is also called the human genome (3.3 × 109bp). The diploid content of human DNA is about 6.6 × 109 bp.

“dna questions “

Question 13. If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6 ×10 9 bp then the length of the DNA is approximately

  1. 2.5 m
  2. 2.2 m
  3. 2.7 m
  4. 2.0 m

Answer: 4. 2.0 m

The distance between two consecutive base pairs is 0.34 nm (0.34×10−9m). The length of the DNA double helix in a typical mammalian cell can be calculated by multiplying the total number of bp with the distance between the two consecutive bp, i.e. 6.6 ×109 bp × 0 34 10. × −9 m/bp = 2.2 m (the length of DNA). Thus, the option is correct.

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Question 14. Which among the following pairs of nitrogen bases are correct?

  1. A=C, T=G
  2. A=T, C=G
  3. A=G, C=T
  4. All of the above

Answer: 2. A=T, C=G

According to Chargaff’s rules, the molar amount of adenine is always equal to the molar amount of thymine. Similarly, the molar concentration of guanine is equal to the molar concentration of cytosine

Question 15. Adenine pairs with thymine through

  1. One hydrogen bond
  2. Two hydrogen bonds
  3. One phosphate bond
  4. Four hydrogen bonds

Answer: 2. two hydrogen bonds

Adenine always pairs with thymine through two hydrogen bonds in DNA.

Similarly, adenine pairs with uracil through two hydrogen bonds in RNA. Guanine and cytosine always pair with three hydrogen bonds.

“dna questions “

Question 16. The diameter of the double helix of DNA is

  1. 34Å
  2. 20Å
  3. 3.4Å
  4. 340Å

Answer: 2. 20Å

The double helix of DNA is of constant diameter of 2 nanometers or 20 Å (angstrom).

Question 17. Purines found both in DNA and RNA are

  1. Adenine and thymine
  2. Adenine and guanine
  3. Guanine and cytosine
  4. Cytosine and thymine

Answer: 2. adenine and guanine

Purines found both in DNA and RNA are adenine and guanine.

Question 18. The left-handed form of DNA is called

  1. A-DNA
  2. cDNA
  3. B-DNA
  4. Z-DNA

Answer: 4. Z-DNA

Z-DNA is left-handed DNA. It is a double helical structure. The phosphate backbone of Z-DNA follows a zig-zag course. The helix of Z-DNA is 18 Å in diameter containing 12 base pairs per turn and one complete turn of helix is 45 Å long.

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Question 19. One turn of the helix in a B-form DNA is approximately

  1. 2 nm
  2. 20 ìm
  3. 0.34 nm
  4. 3.4 nm

Answer: 4. 3.4 nm

B-DNA is right-handed DNA. Here, the double strand is coiled plectonemically in a right-handed fashion around a common axis like a rope staircase twisted in a spiral.

The pitch of the helix per turn is 3.4 nm. The diameter of the helix is 20Å. 10 base pairs are present per turn of the helix.

“dna questions “

Question 20. Which of the following is the common type of DNA present in all organisms?

  1. A type DNA
  2. B type DNA
  3. C type DNA
  4. Z type DNA

Answer: 2. B type DNA

B-form DNA is a right-handed double helix, which was discovered by Watson and Crick based on X-ray diffraction patterns. It is the common form of DNA that exists under normal physiological conditions.

Question 21. Z-DNA is

  1. Right-handed and has about 12 bases per turn
  2. Left-handed and has about 12 bases per turn
  3. Right-handed and has about 10 bases per turn
  4. Left-handed and has about 10 bases per turn

Answer: 2. left-handed and has about 12 bases per turn

Z-DNA is left-handed DNA. It is a double helical structure. The phosphate backbone of Z-DNA follows a zig-zag course. The helix of Z-DNA is 18 Å in diameter containing 12 base pairs per turn and one complete turn of helix is 45 Å long.

Question 22. In a DNA strand of length 340 Å, there are

  1. 100 nucleotides
  2. 100 base pairs
  3. 100 nitrogenous bases
  4. 100 sugar phosphates

Answer: 2. 100 base pairs

“dna questions “

Distance between consecutive bases is 3.4 Å. 340 Å means, it has 340/3.4 = 100 base pairs.

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Question 23. A-DNA is WB

  1. Left-Handed Helix With 12 Nucleotide Pairs Per Turn
  2. Right-Handed Helix With 11 Nucleotide Pairs Per Turn
  3. Right-Handed Helix With 12 Nucleotide Pairs Per Turn
  4. Left-Handed Helix With 11 Nucleotide Pairs Per Turn

Answer: 2. right-handed helix with 11 nucleotide pairs per turn

A-DNA is a right-handed double helix, made up of deoxyribonucleotides. The two strands of A-DNA are antiparallel with each other and not symmetrical.

The molecule is asymmetrical because the glycosidic bonds of a base pair are not diametrically opposite to each other. Therefore, major grooves and minor grooves can be observed in each turn. One turn of the helix consists of 11 base pairs with a length of 2.86 nm.

Question 24. Consider the following statements about A-DNA.

  1. It appears when the relative humidity in the environment is less than 75%.
  2. Its backbone is formed by sugar and phosphates linked by phosphodiester bonds.
  3. The helix width of A-DNA is 0.3 nm.
  4. A-DNA is narrower than B-DNA.

Choose the option representing incorrect statements.

  1. 1 and 2
  2. 3 and 4
  3. 2 and 3
  4. 2, 3 and 4

Answer: 2. 3 and 4

Statements 3 and 4 are incorrect and can be corrected as The helix width of A-DNA is 2.3 nm. Overall, A-DNA is wider than the commonly found B-DNA. Rest statements are correct about A-DNA.

Question 25. Pyrimidines are

  1. Monocyclic
  2. Dicyclic
  3. Tetracyclic
  4. Tricyclic

Answer: 1. Monocyclic

Pyrimidines are monocyclic means, they have one ring of atoms in their molecule.

Question 26. Given below are various types of DNA and their characteristics.

  1. Z-DNA – Right-handed helix
  2. B-DNA – Right-handed helix
  3. A-DNA – Left-handed helix

Choose the option containing incorrectly matched pairs.

“dna questions “

1 and 2
2 and 3
1 and 3
1, 2 and 3

Answer: 3. 1 and 3

Pairs 1 and 3 are incorrectly matched and can be corrected as Z-DNA is a left-handed helix whereas A-DNA is a right-handed helix. 2 is a correctly matched pair.

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Question 27. Identify the wrong statement about DNA.

  1. The length of DNA is defined as the number of base pairs present in it
  2. Cytosine is common to both DNA and RNA
  3. In a nucleotide, the nitrogenous base is linked to a phosphate group
  4. Thymine is chemically 5-methyl uracil
  5. Deoxythymidine is a nucleoside

Answer: 3. In a nucleotide, the nitrogenous base is linked to a phosphate group

The statement in option (3) is wrong. In a nucleotide, the nitrogenous base is linked to the sugar molecule at first carbon by a glycosidic bond. Rest statements are right

Question 28. Match the following columns.

NEET Biology The DNA MCQs Question 28 Match The following columns

Answer: 1–3, 2–1, 3–2

Question 29. The amount of purines is equal to the number of pyrimidines suggested by

  1. Robert Brown
  2. Meischer
  3. Chargaff
  4. Khorana

Answer: 3. Chargaff

Chargaff suggested that purine and pyrimidine base pair are in equal amounts in nucleic acids, i.e. Adenine + Guanine = Thymine + Cytosin

Question 30. The purine-to-pyrimidine ratio in a DNA molecule is

  1. 1: 1
  2. Need not be 1: 1
  3. 1: 2
  4. 2: 1

Answer: 1. 1: 1

Chargaff’s rules state that DNA from any cell of any organism should have a 1:1 ratio (base pair rule) of pyrimidine and purine bases. More specifically, the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.

Question 31. Which one of the following ratios is constant in the DNA of different species?

  1. A + T/C+G
  2. A + G/T+C
  3. A + C/U+G
  4. A + U/C+G

Answer: 1. A + T/C+G

According to the Chargaff rule, in DNA, there is always equality in quantity between the bases A and T and between the bases G and C (A is adenine, T is thymine, G is guanine and C is cytosine). So, A+T: C+G ratio is constant in the DNA of different species

Question 32. In a DNA, the percentage of thymine is 20% then what will be the percentage of guanine?

  1. 20%
  2. 40%
  3. 30%
  4. 60%

Answer: 3. 30%

According to Chargaff’s rule, the ratio of purine bases to pyrimidine bases is equal. A=T;C=G. If T is 20% then A is 20% and C and G are 30% each.

Question 33. The backbone of DNA molecule is formed by

  1. Alternate sugar – po4 – sugar component joined by a phosphodiester bond
  2. Alternate sugar – po4 – sugar component joined by alternate glycoside c bond
  3. Alternate sugar – po4 – sugar component joined by alternate peptide – sulfate bond
  4. Polypeptide linkage

Answer: 1. alternate sugar – PO4 – sugar component joined by a phosphodiester bond

The backbone of DNA is made up of alternating deoxyribose sugar and phosphate groups. They are connected through phosphodiester bonds.

Question 34. In the polynucleotide chain of DNA, a nitrogenous base is linked to the – OH of

  1. 2 C′ pentose sugar
  2. 3 C′ pentose sugar
  3. 5 C′ pentose sugar
  4. 1 C′ pentose sugar

Answer: 4. 1 C′ pentose sugar

NEET Biology The DNA MCQs 34 DNA

In a DNA polynucleotide chain, a nitrogenous base is linked to the hydroxy group (– OH) at 1′ C of pentose sugar. It is represented in the structure given below

Question 35. Phosphodiester linkage is formed between

  1. C-3 of one nucleotide and c-5 of the next
  2. C-l of one nucleotide and c-2 of the next
  3. Purines of opposite strands
  4. Pyrimidines of opposite strands

Answer: 1. C-3 of one nucleotide and C-5 of the next

In DNA and RNA, the phosphodiester bond is the linkage between the 3′ 3-carbon atom of one sugar molecule and the 5′ carbon atom of another.

The sugar molecule is deoxyribose in DNA and ribose in RNA. Strong covalent bonds form between the phosphate group and two 5-carbon ring carbohydrates (pentoses) over two ester bonds

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Question 36. Nitrogenous bases are linked to sugar by

  1. Hydrogen bond
  2. Phosphodiester bond
  3. N-glycosidic bond
  4. Covalent bond

Answer: 3. N-glycosidic bond

Nitrogenous bases are linked to sugar by N-glycosidic bonds.

Question 37. Nucleotides are building blocks of nucleic acids. Each nucleotide is a composite molecule formed by

  1. (Base-sugar-phosphate) N
  2. Base-sugar-OH
  3. Base-sugar-phosphate
  4. Sugar-phosphate

Answer: 3. Base-sugar-phosphate

Nucleotides are the building blocks or monomeric units. Each nucleotide contains nitrogen bases (purines and pyrimidines), pentose sugar (5C), and a phosphate group

Question 38. Which of the following is a nucleoside?

  1. Adenosine
  2. Adenine
  3. Deoxyribose
  4. Adenylic acid

Answer: 1. Adenosine

Molecular Basis Of Inheritance Nucleoside

Nucleoside is formed when the nitrogenous bases are linked to sugar. These include adenosine, guanosine, cytidine, etc. So in the given options, adenosine is a nucleoside

Question 39. The charge on DNA is

  1. Negative
  2. Positive
  3. No charge
  4. Both +ve and –ve

Answer: 1. negative

DNA has a negative charge due to the negative charge of its phosphate component.

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Question 40. Nucleoside means

  1. Sugar + nitrogen base
  2. Nucleotide + phosphate
  3. Deoxyribose sugar + n base
  4. Both purines and pyrimidines

Answer: 1. Both purines and pyrimidines

A pentose sugar when attached tothe nitrogen base, either a purine or a pyrimidine is called a nucleoside. It does not contain a phosphate group.

Question 41. A nucleosome is the repeating unit of …………….. in a nucleus.

  1. Chromosome
  2. Genes
  3. Chromatin
  4. Chromatosome

Answer: 3. chromatin

Chromatins are thread-like stained (colored) bodies seen in the nucleus. The nucleosome is a repeating unit in chromatin and is seen as ‘beads on a string’ when viewed under an electron microscope.

Question 42. The diameter of nucleosome fiber is

  1. 30 nm
  2. 20 nm
  3. 10 nm
  4. 40 nm

Answer: 3. 10 nm

DNA is wrapped around a core of histones, forming a nucleosome fiber of about 10 nm diameter.

Question 43. Nucleosome consists of

  1. Nucleolus
  2. Genes
  3. Microfilaments
  4. Histones

Answer: 4. histones

Histones are the main structural proteins found in eukaryotic cells. The nucleosome core is made up of four types of histone proteins, i.e. H A2, H B2, H3, and H4 occurring in pairs.

200 bp of DNA helix wraps around the nucleosome by turns, plugged by H1 histone protein. So, nucleosome consists of histones

Question 44. Five types of histone proteins are

  1. H1, H2A, H2C, H2D and H3A
  2. H1, H2A, H2B, H3 and H4
  3. H1, H2A, H2B, H3A and H4
  4. H1, H2A, H2B, H3 and H5

Answer: 2. H1, H2A, H2B, H3 and H4

Histones are the main structural proteins found in eukaryotic cells. The nucleosome core is made up of four types of histone proteins, i.e. H A2, H B2, H3, and H4 occur in pairs. 200 bp of DNA helix wraps around the nucleosome by turns, plugged by H1 histone protein. So, nucleosome consists of histones

Question 45. The number of nucleosomes present in a human cell is

  1. 3.3 × 107 nucleosome
  2. 1.1 × 107 nucleosome
  3. 6.6 × 107 nucleosome
  4. Indefinite

Answer: 1. 3.3 × 107 nucleosome

Approximately 200 bp are present per nucleosome. The total number of base pairs in human genetic material is =6.6 × 109. Number of nucleosomes

Question 46. The packaging of chromatin at a higher level requires an additional set of proteins that are collectively referred to as

  1. Histone proteins
  2. Non-histone proteins
  3. Basic proteins
  4. Histone octamer

Answer: 2. non-histone proteins

The packaging of chromatin at a higher level requires an additional set of basic proteins called non-histone proteins.

These are heterogeneous groups of proteins that play important roles in nucleosome remodeling, DNA processing, etc.

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Question 47. The densely packed and transcriptionally inactive part of chromatin is

  1. Euchromatin
  2. Heterochromatin
  3. Solenoid fibre
  4. NHC

Answer: 2. heterochromatin

In some places, chromatin is densely packed to form darkly stained heterochromatin. It is transcriptionally inactive.

Question 48. The lightly stained part of chromatin which remains loosely packed is

  1. Euchromatin
  2. Heterochromatin
  3. Chromatosome
  4. Chromonemata

Answer: 1. euchromatin

The loosely packed form of DNA in the chromosome is called it is euchromatin.

In heterochromatin, the density of DNA is high and it is stained dark, whereas in euchromatin, the density of DNA is low and it is lightly stained.

Question 49. The association of histone H1 with a nucleosome indicates

  1. Transcription is occurring
  2. Dna replication is occurring
  3. The dna is condensed into a chromatin fibre
  4. The dna double helix is exposed

Answer: 3. The DNA is condensed into a chromatin fiber

The association of H1 protein indicates the complete formation of nucleosomes in which DNA is condensed into chromatin fiber.

Question 50. Which amino acids are present in histones?

  1. Lysine and histidine
  2. Valine and histidine
  3. Arginine and lysine
  4. Arginine and histidine

Answer: 3. Arginine and lysine

Histones are alkaline proteins that wrap DNA into a condensed form. They consist of two basic (positively charged) amino acids, arginine and lysine.

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Question 51. Linker DNA is

  1. A part of nucleosome
  2. A part that joins two octamer cores
  3. Ssdna
  4. Both (1) and (2)

Answer: 4. Both (1) and (2)

Linker DNA is double-stranded DNA, 38-53 bp long in between two nucleosome cores that in association with histone H1, hold the cores (octamer) together. Linker DNA is seen as the string in the beads and string model. Thus, the option is correct

Question 52. In the given diagram, identify A B, and C.

NEET Biology The DNA MCQs Core of histone molecules

  1. A–DNA, B–H1 histone, C–Histone octamer
  2. A–RNA, B–Cistron, C–DNA
  3. A–DNA, B–H3 histone, C–Histone tetramer
  4. A–RNA, B–H1 histone, C–Histone octamer

NEET Biology The DNA MCQs Core of histone molecules answer

Answer: 1. A–DNA, B–H1 histone, C–Histone octamer

Question 53. The sequence of nitrogenous bases in one strand of DNA is 3 ′-TAC GCG ACG- 5 ′. The complementary DNA strand should have Karnataka

  1. 5′- AUG CGC TGC- 3′
  2. 3′ – ATG CGC TGC- 5′
  3. 5′ – UAC GCG ACG- 3′
  4. 5′- ATG CGC TGC- 3

Answer: 4. 5′- ATG CGC TGC- 3

Two strands of DNA molecules are held together by hydrogen bonds between their bases.

Adenine (A), a purine of one chain lies exactly opposite thymine (T), a pyrimidine of the other chain. Similarly, cytosine (C, a pyrimidine) lies opposite guanine (G, a purine). Thus, the complementary strand would be 5′- ATG CGC TGC – 3

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