Two among the three components of DNA are β-D-2-deoxyribose and a heterocyclic base. The third component is: (

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CBSECBSE Class XII Board 2024MCQ· 1mImportance★★★★★

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Concept understanding — Nucleic Acid Components

Nucleic Acid Components: The Alphabet of Life

Imagine you want to write a book that contains all the instructions for building and running a living organism. You'd need an alphabet — a set of letters that can be combined in endless ways to form words, sentences, and chapters. In living cells, that alphabet is made of nucleic acids (DNA and RNA), and each "letter" is called a nucleotide.

The Big Picture: What Are Nucleic Acids?

Nucleic acids are long, chain-like molecules that store and transmit genetic information. DNA holds the master blueprint; RNA helps execute it. But both are built from the same basic building block: the nucleotide.

Note

Think of a nucleotide as a single Lego brick. DNA and RNA are long chains of these bricks, each brick slightly different from the next.

The Three Parts of a Nucleotide

Every nucleotide has three components, like a three-part key:

A phosphate group — a small, negatively charged group ( $\text{PO}_4^{3-}$ ). It acts like the "handle" that links nucleotides together.
A sugar — either ribose (in RNA) or deoxyribose (in DNA). This is the "body" of the brick.
A nitrogenous base — a ring-shaped molecule containing nitrogen. This is the "colored part" that carries the actual information.

The sugar and base together form a nucleoside. When you add the phosphate, you get a nucleotide.

Nucleoside = Sugar + Base Nucleotide = Sugar + Base + Phosphate

The Two Families of Bases

The bases come in two structural types:

Purines (double-ring structures): Adenine (A) and Guanine (G)
Pyrimidines (single-ring structures): Cytosine (C), Thymine (T) (only in DNA), and Uracil (U) (only in RNA)

Tip

A mnemonic: Purines are Pure as All Gold (A and G). Pyrimidines are CUT (C, U, T).

DNA vs. RNA: The Key Differences

Feature	DNA	RNA
Sugar	Deoxyribose (missing one oxygen)	Ribose (has that oxygen)
Bases	A, G, C, T	A, G, C, U
Structure	Double-stranded helix	Usually single-stranded
Function	Stores genetic information	Carries and executes instructions

Watch out

A common mistake: thinking "nucleoside" and "nucleotide" are the same. Remember: nucleotide has the phosphate; nucleoside does not. ATP (adenosine triphosphate) is a nucleotide — it's the energy currency of the cell.

Why This Matters

The sequence of bases along a DNA strand spells out the genetic code. A change in even one base (a mutation) can alter a protein, sometimes with dramatic consequences — like sickle cell anemia, where a single base change in the hemoglobin gene causes red blood cells to deform.

The Precise Statement

Important

Nucleic acid components are the molecular subunits — nucleotides — that polymerize to form DNA and RNA. Each nucleotide consists of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base (purine or pyrimidine). The specific sequence of these bases encodes genetic information.

Quick Check: Can You Identify?

If I give you a molecule with ribose, adenine, and a phosphate — is it a nucleoside or a nucleotide?

Answer: It's a nucleotide (it has all three parts). If the phosphate were missing, it would be a nucleoside (adenosine).

Start with this framework, and the rest of molecular biology — replication, transcription, translation — will fall into place. The alphabet is simple; the stories it tells are infinite.

"Nucleic acid components nucleotide structure" and "molecular basis of inheritance class 12 biology" are commonly searched terms, both grounded in the Molecular Basis of Inheritance chapter of the NCERT/CBSE Class 12 Biology curriculum. Differentiating nucleoside from nucleotide, and DNA from RNA components, is a frequent short-answer question in board exams and NEET.

Why this formula?

Nucleic Acid Components: Understanding the "Why" Behind the Key Relationships

Let’s start with the big picture: Nucleic acids (DNA and RNA) are polymers made of nucleotides. Each nucleotide has three parts: a nitrogenous base, a pentose sugar, and a phosphate group. The key formulas and relationships in this topic arise from how these parts are linked and how they behave chemically.

1. The Basic Composition Formula

What it says:

A nucleotide = Base + Sugar + Phosphate

Why this holds:

Chemical necessity: The sugar (ribose in RNA, deoxyribose in DNA) has a 5-carbon ring. The base attaches to the 1' carbon (via a glycosidic bond), and the phosphate attaches to the 5' carbon (via an ester bond).
Directionality: This creates a 5' → 3' linkage in the polymer. The phosphate of one nucleotide bonds to the 3' carbon of the next sugar.
Reasoning: Without the phosphate, you have a nucleoside (base + sugar). Adding the phosphate makes it a nucleotide — the monomer that can polymerize.

Key takeaway: The formula isn’t arbitrary — it reflects the specific carbon positions on the sugar that allow for stable, directional chain formation.

2. Chargaff’s Rules (for DNA)

What it says:

In double-stranded DNA:

$[A] = [T]$
$[G] = [C]$
$[A] + [G] = [T] + [C]$

Why this holds:

Base pairing: Adenine (A) forms two hydrogen bonds with Thymine (T). Guanine (G) forms three hydrogen bonds with Cytosine (C).
Structural constraint: The DNA double helix has a constant width (20 Å). A purine (A or G) always pairs with a pyrimidine (T or C) — otherwise the helix would bulge or narrow.
Derivation: If every A on one strand must pair with a T on the opposite strand, then the number of A equals number of T in the whole molecule. Same for G and C.
Consequence: The sum of purines equals sum of pyrimidines ( $A+G = T+C$ ).

Why it’s not just a rule: It’s a geometric and energetic necessity — hydrogen bonding and helix stability force this equality.

3. The Phosphodiester Bond Energy Formula

What it says:

Formation of a phosphodiester bond requires ~30 kJ/mol of energy (from ATP).

Why this holds:

Mechanism: The 3' hydroxyl of one nucleotide attacks the α-phosphate of a nucleotide triphosphate (e.g., ATP). This releases pyrophosphate (PPi).
Energy source: The hydrolysis of PPi to two inorganic phosphates ( $PPi \rightarrow 2P_i$ ) is highly exergonic (ΔG ≈ -30 kJ/mol). This drives the reaction forward.
Reasoning: The bond itself is a covalent ester linkage — strong but not spontaneously formed. The energy comes from breaking a high-energy phosphate bond in the triphosphate.

Key insight: The formula isn’t about the bond’s strength — it’s about the thermodynamic cost of making it in a cell.

4. The Melting Temperature ( $T_m$ ) Formula

What it says:

$T_m$ (in °C) ≈ $4(G+C) + 2(A+T)$ for short oligonucleotides.

Why this holds:

Hydrogen bonds: G-C pairs have 3 H-bonds, A-T pairs have 2 H-bonds. More H-bonds = more energy needed to separate strands.
Stacking interactions: G-C base pairs also have stronger π-stacking (aromatic ring overlap) than A-T.
Derivation: The formula is empirical — it comes from measuring $T_m$ for many sequences. The coefficients (4 and 2) reflect the relative stability contributed by each base pair.
Limitation: For long DNA, this simple formula fails because nearest-neighbor interactions matter more.

Why it works: It’s a linear approximation of the free energy needed to break all base pairs, weighted by H-bond count.

5. The Central Dogma (Information Flow)

What it says:

DNA → RNA → Protein

Why this holds:

Chemical stability: DNA is chemically stable (deoxyribose lacks a 2'-OH, making it resistant to hydrolysis). It’s the permanent archive.
Transcription: RNA is transient (ribose has a 2'-OH, making it more reactive). It’s the working copy.
Translation: Proteins are the functional molecules — they do the work. The genetic code (triplet codons) maps RNA to amino acids.
Reasoning: This flow is unidirectional because DNA cannot be directly read by ribosomes (too large, too stable), and RNA cannot be reverse-transcribed into DNA in most cells (except retroviruses).

Key formula: The genetic code is a 3-letter code (codon) → 1 amino acid. $4^3 = 64$ codons for 20 amino acids + stop signals.

Summary Table of Key Relationships

Concept	Formula/Relationship	Why It Holds
Nucleotide composition	Base + Sugar + Phosphate	Specific carbon positions (1', 5') enable polymerization
Chargaff’s rules	$A=T$ , $G=C$ , $A+G=T+C$	Hydrogen bonding and helix geometry
Bond energy	~30 kJ/mol from ATP	Pyrophosphate hydrolysis drives ester bond formation
Melting temperature	$T_m \approx 4(G+C) + 2(A+T)$	H-bond count and stacking interactions
Central dogma	DNA → RNA → Protein	Chemical stability and functional roles

Final thought: Every formula in nucleic acid chemistry is rooted in molecular geometry (which atoms can bond where), thermodynamics (which reactions are favorable), and evolutionary constraints (stability vs. flexibility). Memorize the formulas, but always ask: What physical or chemical principle forces this to be true?

DNA is built from three components: a sugar (deoxyribose), a phosphate group, and a nitrogenous base. The third component here is phosphoric acid, which forms the backbone of the DNA strand.

The question tests your understanding of the basic building blocks of nucleic acids. DNA and RNA are polymers — long chains of repeating units called nucleotides. Each nucleotide has three parts: a sugar, a phosphate, and a base. The sugar in DNA is $\beta$ -D-2-deoxyribose, and the bases are heterocyclic compounds (like adenine, guanine, cytosine, thymine). The third component, which links the sugars together, is a phosphate group derived from phosphoric acid.

Let’s break it down:

Identify what’s already given.

The problem states that two components are $\beta$ -D-2-deoxyribose (the sugar) and a heterocyclic base. That leaves the third component — the one that connects nucleotides into a chain.
Recall the structure of a nucleotide.

A DNA nucleotide consists of:
- A pentose sugar (deoxyribose)
- A nitrogenous base (adenine, guanine, cytosine, or thymine)
- A phosphate group ( $\text{PO}_4^{3-}$ ), which comes from phosphoric acid ( $\text{H}_3\text{PO}_4$ )
The phosphate group forms a phosphodiester bond between the 3' carbon of one sugar and the 5' carbon of the next, creating the sugar-phosphate backbone.
Eliminate the wrong options.
- (A) Adenine — This is a heterocyclic base, already covered by “a heterocyclic base” in the question. So it cannot be the third component.
- (C) Sulphuric acid — Not a component of DNA. Sulfur is found in some proteins (e.g., cysteine) but not in the DNA backbone.
- (D) Uracil — This is a base found in RNA, not DNA. DNA uses thymine instead of uracil.
Confirm the correct option.

The third component is the phosphate group, which is derived from phosphoric acid. In biological contexts, we often say “phosphate” or “phosphoric acid” interchangeably when referring to the source of the phosphate group in nucleotides.

Watch out

A common mistake is to think of “phosphoric acid” as a separate molecule floating in the cell. In DNA, the phosphate is covalently bonded to the sugar — it’s not free acid. But the question uses “phosphoric acid” to mean the source of the phosphate group, which is standard in such exam questions.

Tip

Remember the mnemonic: DNA = Deoxyribose + Nitrogenous base + Acid (phosphoric). The “acid” part is often overlooked, but it’s essential for the backbone.

✓Final answer

The correct option is (B) Phosphoric acid .

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 39 on this concept.

CBSE 2026Set 56/2/11 markMCQ
$Q. The base which is present in DNA but not in RNA is : (A) Guanine (B) Cytosine (C) Thymine (D) Adenine$
›Reveal solutionSolution
The key difference between DNA and RNA is that DNA contains thymine (T) while RNA contains uracil (U) in its place. The base present in DNA but absent in RNA is thymine, which corresponds to option (C).

Why This Question Tests a Fundamental Distinction

DNA and RNA are both nucleic acids, but they serve different roles in the cell — DNA stores genetic information, while RNA helps express it. One of the clearest chemical differences between them lies in their nitrogenous bases. Both use adenine (A), guanine (G), and cytosine (C), but they differ in the fourth base: DNA uses thymine (T), and RNA uses uracil (U). This is not a trivial detail — it affects base pairing, stability, and even how enzymes distinguish the two molecules.

The question asks you to spot which base is exclusive to DNA. Let’s walk through the reasoning.

List the bases common to both DNA and RNA.

Adenine (A), guanine (G), and cytosine (C) appear in both nucleic acids. So options (A), (B), and (D) are present in RNA as well — they cannot be the answer.

Identify the base unique to DNA.

Thymine (T) is found in DNA but is replaced by uracil (U) in RNA. This substitution is a defining chemical difference. Therefore, thymine is the base present in DNA but not in RNA.

Confirm by elimination.

Guanine (A): present in both.

Cytosine (B): present in both.

Thymine (C): present only in DNA.

Adenine (D): present in both.

Watch out

A common mistake is to confuse uracil with thymine. Remember: uracil is RNA-only, thymine is DNA-only. They are structurally similar (both are pyrimidines), but thymine has a methyl group that uracil lacks.

Tip

A quick memory aid: "DNA has T, RNA has U" — think of "T" for "Thymine" and "U" for "Uracil". Also, the mnemonic "A-T-G-C" for DNA base pairs reminds you that T belongs to DNA.

✓Final answer
$The correct option is (C) Thymine .$
CBSE 2026Set ANNUAL1 markMCQ
$Q. Which of the following is not a pyrimidine base?$
(a) Adenine
(b) Uracil
(c) Thymine
(d) Cytosine
›Reveal solutionSolution
Adenine is a purine, not a pyrimidine; the other three listed bases (cytosine, uracil, thymine) are pyrimidines.

Nitrogenous bases found in nucleic acids are classified into two structural families:

Purines: fused bicyclic (six-membered + five-membered ring) heterocycles — these are Adenine (A) and Guanine (G).

Pyrimidines: single six-membered heterocyclic ring — these are Cytosine (C), Thymine (T, found in DNA), and Uracil (U, found in RNA in place of thymine).

Of the given options, cytosine, uracil, and thymine are all pyrimidine derivatives (single-ring), while adenine is a purine (double-ring, fused with an imidazole ring), so it does not belong to the pyrimidine group.

✓Final answer
$(a) Adenine is NOT a pyrimidine base — it is a purine.$
CBSE 2026Set ANNUAL1 mark
$Q. Write any one difference between DNA and RNA.$
›Reveal solutionSolution

DNA and RNA differ in their sugar component, strand structure, and one nitrogenous base.

One clear structural difference: the sugar in DNA is deoxyribose (lacking an -OH at C2'), whereas the sugar in RNA is ribose (has an -OH at C2'). (Other valid differences: DNA is usually double-stranded/helical while RNA is usually single-stranded; DNA has thymine as a base while RNA has uracil in place of thymine.)

✓Final answer
$DNA contains deoxyribose sugar; RNA contains ribose sugar.$
CBSE 2026Set ANNUAL1 mark
$Q. Read the following paragraph and answer the question given below: Complete hydrolysis of DNA/RNA gives a pentane sugar, phosphoric acid and nitrogen containing heterolysis base. In DNA, sugar is β-D-2-deoxyribose and in RNA, sugar is β-D-ribose. DNA has four bases i.e. adenine, guanine, cytosine and thymine. In RNA instead of thymine, the bases is uracil and other three bases are same. Base attached to sugar forms nucleoside, while, sugar molecule joined to phosphate group and base forms nucleotide.$
(i) Name the bases present in RNA.
›Reveal solutionSolution

RNA's four bases are adenine, guanine, cytosine and uracil.

Nucleic acids are built from purine and pyrimidine bases attached to a sugar-phosphate backbone. The purines (adenine and guanine) are common to both DNA and RNA. Among the pyrimidines, DNA uses cytosine and thymine, while RNA uses cytosine and uracil in place of thymine (uracil lacks the methyl group present on thymine).

✓Final answer
$The bases present in RNA are adenine, guanine, cytosine and uracil.$
CBSE 2026Set ANNUAL1 mark
$Q. Read the following paragraph and answer the question given below: Complete hydrolysis of DNA/RNA gives a pentane sugar, phosphoric acid and nitrogen containing heterolysis base. In DNA, sugar is β-D-2-deoxyribose and in RNA, sugar is β-D-ribose. DNA has four bases i.e. adenine, guanine, cytosine and thymine. In RNA instead of thymine, the bases is uracil and other three bases are same. Base attached to sugar forms nucleoside, while, sugar molecule joined to phosphate group and base forms nucleotide.$
(ii) What is nucleotide?
›Reveal solutionSolution

A nucleotide = nitrogenous base + pentose sugar + phosphate group.

When a nitrogenous base (purine or pyrimidine) is attached to the pentose sugar (ribose or deoxyribose) through a $\beta$ -N-glycosidic bond, the unit formed is called a nucleoside. When the 5'-OH of this sugar is further esterified with phosphoric acid, the resulting base-sugar-phosphate unit is called a nucleotide. Nucleotides are the repeating monomer units that are joined by phosphodiester bonds to form the polynucleotide chain of DNA or RNA.

✓Final answer
$A nucleotide is a base + sugar + phosphate group linked together (the phosphate ester of a nucleoside); nucleotides are the monomers of DNA/RNA.$
CBSE 2026Set ANNUAL1 mark
$Q. Read the following paragraph and answer the question given below: Complete hydrolysis of DNA/RNA gives a pentane sugar, phosphoric acid and nitrogen containing heterolysis base. In DNA, sugar is β-D-2-deoxyribose and in RNA, sugar is β-D-ribose. DNA has four bases i.e. adenine, guanine, cytosine and thymine. In RNA instead of thymine, the bases is uracil and other three bases are same. Base attached to sugar forms nucleoside, while, sugar molecule joined to phosphate group and base forms nucleotide.$
(iii) Name the sugar present in DNA.
›Reveal solutionSolution

DNA's sugar is $\beta$ -D-2-deoxyribose (lacks an -OH at the 2' carbon).

DNA and RNA differ in the pentose sugar of their backbone. DNA contains $\beta$ -D-2-deoxyribose, in which the 2'-carbon of the ribose ring bears only hydrogen atoms (no -OH group) — hence the name 'deoxy'. This lack of a 2'-OH makes DNA chemically more stable than RNA, which is one reason DNA is used as the long-term hereditary material.

✓Final answer
$\beta$
CBSE 2026Set ANNUAL1 mark
$Q. Read the following paragraph and answer the question given below: Complete hydrolysis of DNA/RNA gives a pentane sugar, phosphoric acid and nitrogen containing heterolysis base. In DNA, sugar is β-D-2-deoxyribose and in RNA, sugar is β-D-ribose. DNA has four bases i.e. adenine, guanine, cytosine and thymine. In RNA instead of thymine, the bases is uracil and other three bases are same. Base attached to sugar forms nucleoside, while, sugar molecule joined to phosphate group and base forms nucleotide.$
(iv) Name the sugar present in RNA.
›Reveal solutionSolution

RNA's sugar is $\beta$ -D-ribose (has a free -OH at the 2' carbon).

Unlike DNA, RNA retains a hydroxyl group at the 2'-carbon of its pentose sugar, so its sugar is called $\beta$ -D-ribose (not 'deoxy'). This extra -OH group makes the RNA backbone more reactive/less stable than DNA's, which is consistent with RNA's shorter-lived, functional roles (mRNA, tRNA, rRNA) compared with DNA's role as stable, long-term genetic storage.

✓Final answer
$\beta$
CBSE 2026Set ANNUAL1 mark
$Q. Read the following paragraph and answer the question given below: Complete hydrolysis of DNA/RNA gives a pentane sugar, phosphoric acid and nitrogen containing heterolysis base. In DNA, sugar is β-D-2-deoxyribose and in RNA, sugar is β-D-ribose. DNA has four bases i.e. adenine, guanine, cytosine and thymine. In RNA instead of thymine, the bases is uracil and other three bases are same. Base attached to sugar forms nucleoside, while, sugar molecule joined to phosphate group and base forms nucleotide.$
(v) Name the bases present in DNA.
›Reveal solutionSolution

DNA's four bases are adenine, guanine, cytosine and thymine.

DNA carries two purine bases, adenine (A) and guanine (G), and two pyrimidine bases, cytosine (C) and thymine (T). In the DNA double helix these bases pair specifically by hydrogen bonding — A pairs with T (two H-bonds) and G pairs with C (three H-bonds) — which is the structural basis of complementary base pairing.

✓Final answer
$The bases present in DNA are adenine, guanine, cytosine and thymine.$
CBSE 2025Set D1 markMCQ
$Q. The purine base present in RNA is$
(a) Guanine
(b) Thymine
(c) Cytosine
(d) Uracil
›Reveal solutionSolution
Nucleic acid bases are purines (adenine, guanine) or pyrimidines (cytosine, thymine, uracil). The purine in RNA among the options is guanine.

The nitrogenous bases in nucleic acids are of two types:

Purines (two fused rings): Adenine (A) and Guanine (G).

Pyrimidines (single ring): Cytosine (C), Thymine (T) and Uracil (U).

RNA contains A, G, C and U (uracil replaces the thymine of DNA). Of the options, thymine, cytosine and uracil are pyrimidines; only guanine is a purine.

✓Final answer
$(A) Guanine — the purine base present in RNA.$
CBSE 2025Set ANNUAL1 mark
$Q. Draw a diagram of double strand helix structure for DNA.$
›Reveal solutionSolution
Figure — Labelled DNA double helix (Watson-Crick model). Two ANTIPARALLEL sugar-phosphate backbones coiled RI

The Watson-Crick double helix model of DNA: two antiparallel polynucleotide strands wound around a common axis, sugar-phosphate backbone outside, complementary bases paired by hydrogen bonds on the inside.

A labelled diagram of the DNA double helix would show the following key features, described here in place of a drawing:

TWO POLYNUCLEOTIDE STRANDS: each strand is a chain of alternating deoxyribose sugar and phosphate units (the sugar-phosphate backbone), drawn as two continuous ribbons running along the outside of the structure.

ANTIPARALLEL ORIENTATION: the two strands run in opposite directions - one strand 5' -> 3' from top to bottom, the other 3' -> 5' from top to bottom.

RIGHT-HANDED HELIX: the two backbones are coiled around a common central axis in a right-handed spiral (like a twisted ladder).

BASE PAIRS AS RUNGS: nitrogenous bases (Adenine, Thymine, Guanine, Cytosine) are attached to each sugar and project INWARD, pairing across the two strands to form the 'rungs' of the ladder, held together by hydrogen bonds:

Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds

Guanine (G) pairs with Cytosine (C) via 3 hydrogen bonds (This is called complementary base pairing.)

DIMENSIONS: the helix has a diameter of about 20 Angstrom (2 nm); one complete turn of the helix spans about 34 Angstrom (3.4 nm) and contains 10 base pairs.

✓Final answer
$A right-handed double helix of two antiparallel strands, sugar-phosphate backbone outside, bases paired inside by H-bonds (A=T with 2 H-bonds, G\equivC with 3 H-bonds).$
CBSE 2025Set ANNUAL1 markMCQ
$Q. Identify the complementary strand of the DNA primary structure ATGCCGATC.$
(a) AUGCCGAUC
(b) TACGGCJAG
(c) UACGGCUAG
(d) GATCGGCAT
›Reveal solutionSolution

DNA base pairing is complementary and antiparallel-in-composition: A pairs with T, and G pairs with C; applying this rule base-by-base to the given strand gives the complementary strand.

Given strand: 5'-A T G C C G A T C-3'

Applying Watson-Crick complementary base pairing (A<->T, G<->C) to each base in turn:

A->T, T->A, G->C, C->G, C->G, G->C, A->T, T->A, C->G

Complementary strand: T A C G G C T A G

Among the choices, option (b) is printed as 'TACGGCJAG', which matches this result exactly except for an apparent printing/OCR error ('J' instead of 'T' at that position) - once corrected, it reads TACGGCTAG, the correct complementary strand. (Options using U instead of T would represent an RNA transcript, not the DNA complementary strand asked for here.)

✓Final answer
$(b) TACGGCTAG (as printed: 'TACGGCJAG', where 'J' is a typographical error for 'T').$
CBSE 2025Set ANNUAL1 mark
$Q. Read the following paragraph and answer the questions given below: Give full form of DNA and RNA.$
›Reveal solutionSolution
DNA and RNA are the two nucleic acids that store and transmit an organism's genetic information.

Nucleic acids are biopolymers of nucleotides (each nucleotide = a nitrogenous base + a pentose sugar + a phosphate group).

DNA stands for Deoxyribonucleic Acid. It contains the sugar 2-deoxyribose and carries the hereditary information of the organism, transmitted from parents to offspring.

RNA stands for Ribonucleic Acid. It contains the sugar ribose and is mainly responsible for expressing this genetic information, i.e. protein synthesis.

✓Final answer
$DNA = Deoxyribonucleic acid; RNA = Ribonucleic acid.$

Q.Two among the three components of DNA are β\betaβ-D-2-deoxyribose and a heterocyclic base. The third component is: (A) Adenine (B) Phosphoric acid (C) Sulphuric acid (D) Uracil

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Q.Two among the three components of DNA are $\beta$ -D-2-deoxyribose and a heterocyclic base. The third component is:
(A) Adenine
(B) Phosphoric acid
(C) Sulphuric acid
(D) Uracil

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