CUET UG Chemistry Booster Test - 2 Nucleic Acids and Hormones -

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CUET UG Chemistry Booster Test - 1 Nucleic Acids and Hormones

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Chemistry Booster Test - 1 Nucleic Acids and Hormones

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QUESTION 1 OF 20

The study of the chemical processes and complex biomolecules like nucleic acids within a living system falls under the domain of:

Answer Review

1 The study of the chemical processes and complex biomolecules like nucleic acids within a living system falls under the domain of:

A Physical Chemistry

B Biochemistry

C Inorganic Chemistry

D Analytical Chemistry

💡 Short Explanation

�� Biochemistry studies the chemistry of living organisms. �� It deals with biomolecules such as proteins, carbohydrates, lipids and nucleic acids. �� It explains the chemical reactions occurring inside living cells.

✅ Correct Answer Explanation

Biochemistry is the branch of science that studies the chemical composition, structure and reactions occurring in living organisms. It focuses on biomolecules such as nucleic acids, proteins, carbohydrates and lipids, along with the metabolic processes essential for life. Therefore, the study of nucleic acids and other biomolecules within living systems belongs to Biochemistry, making Option B correct.

❓ Why Other Options Are Incorrect

�� Option A → Physical Chemistry deals with the physical principles governing chemical systems, not specifically living organisms.
�� Option C → Inorganic Chemistry mainly studies compounds other than most carbon-containing biomolecules.
�� Option D → Analytical Chemistry focuses on the identification and quantitative analysis of substances rather than biological processes.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Identify the branch of chemistry that specifically studies biomolecules and life processes.

Final Logic:

Biochemistry investigates the chemistry of living organisms; therefore Option B is correct.

🧠 Memory Trick

Bio = Life + Chemistry = Biomolecules

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Introduction to Biomolecules and Biochemistry

2 Arrange the following components in decreasing order of typical carbon atom content based on their standard structures:
(A) Dinucleotide
(B) Nucleotide
(C) Nucleoside
(D) Pentose Sugar

A (A), (B), (C), (D)

B (D), (C), (B), (A)

C (B), (C), (D), (A)

D (A), (C), (B), (D)

💡 Short Explanation

�� A dinucleotide contains two nucleotide units. �� A nucleotide contains a nucleoside and a phosphate group. �� A nucleoside contains a sugar and a nitrogenous base, while a pentose sugar is the simplest among them.

✅ Correct Answer Explanation

A dinucleotide consists of two nucleotide units and therefore has the greatest number of carbon atoms. A nucleotide contains a pentose sugar, a nitrogenous base and a phosphate group. A nucleoside consists of only a sugar and a nitrogenous base, while a pentose sugar alone contains the fewest carbon atoms among the given structures. Hence, the decreasing order is Dinucleotide → Nucleotide → Nucleoside → Pentose Sugar, making Option A correct.

❓ Why Other Options Are Incorrect

�� Option B → Lists the order from least to greatest carbon content.
�� Option C → Incorrectly places nucleotide before dinucleotide.
�� Option D → Places nucleoside before nucleotide, although a nucleotide contains an additional phosphate group as part of a larger molecular structure.

🎯 Strategy

Used

Ordering

Application:

Arrange the biological molecules from the largest molecular structure to the smallest.

Final Logic:

Dinucleotide > Nucleotide > Nucleoside > Pentose Sugar; therefore Option A is correct.

🧠 Memory Trick

Di → Nu → Side → Sugar

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Nucleotides and Nucleosides

3 Which of the following best describes the chemical naming and structure of the sugar found in DNA compared to RNA?

A It contains an extra oxygen atom at the 2' position.

B It lacks an oxygen atom at the 2' position, hence "2-deoxyribose".

C It is a hexose sugar instead of a pentose sugar.

D It is a straight-chain aldose in its native form.

💡 Short Explanation

�� DNA contains 2-deoxyribose sugar. �� It differs from ribose by the absence of an oxygen atom at the 2′ carbon. �� RNA contains ribose, whereas DNA contains deoxyribose.

✅ Correct Answer Explanation

The pentose sugar present in DNA is β-D-2-deoxyribose, which differs from the ribose present in RNA because it lacks an oxygen atom at the 2′ carbon atom. This absence of oxygen gives the sugar its name 2-deoxyribose and contributes to the greater chemical stability of DNA. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → DNA lacks, rather than contains, the oxygen atom at the 2′ carbon.
�� Option C → DNA contains a pentose sugar, not a hexose sugar.
�� Option D → In nucleic acids, the sugar exists predominantly in a cyclic (furanose) form rather than a straight-chain form.

🎯 Strategy

Used

Direct Recall

Application:

Recall the structural difference between the sugars present in DNA and RNA.

Final Logic:

DNA contains 2-deoxyribose, which lacks the oxygen atom at the 2′ carbon; therefore Option B is correct.

🧠 Memory Trick

DNA = Deoxy = One Oxygen Less

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Pentose Sugars in DNA and RNA

4 What is the fundamental biological process/reaction type by which DNA maintains the identity of different species over millions of years?

A Transcription

B Self-duplication during cell division

C Denaturation under heat

D Hydrolysis into basic nucleotides

💡 Short Explanation

�� DNA carries hereditary information. �� DNA replicates before every cell division. �� This ensures faithful transmission of genetic information from one generation to the next.

✅ Correct Answer Explanation

DNA maintains the continuity of hereditary information through self-duplication (DNA replication) before cell division. During replication, each DNA molecule produces an identical copy, ensuring that daughter cells inherit the same genetic information. This faithful transmission preserves the identity of species across generations. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → Transcription produces RNA from DNA but does not transmit hereditary information during cell division.
�� Option C → Denaturation separates DNA strands and is not responsible for species continuity.
�� Option D → Hydrolysis breaks DNA into smaller components rather than preserving genetic information.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Identify the biological process responsible for inheritance and continuity of genetic information.

Final Logic:

DNA replication ensures genetic continuity; therefore Option B is correct.

🧠 Memory Trick

DNA Replicates = DNA Remains

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: DNA Replication and Heredity

5 Match the specific RNA type with its functional characteristic:

List I	List II
1. — m-RNA	a. — Transfer RNA
2. — t-RNA	b. — Ribosomal RNA
3. — r-RNA	c. — Messenger RNA

A (1)-(c), (2)-(a), (3)-(b)

B (1)-(a), (2)-(b), (3)-(c)

C (1)-(b), (2)-(c), (3)-(a)

D (1)-(c), (2)-(b), (3)-(a)

💡 Short Explanation

�� m-RNA carries genetic information. �� t-RNA transfers amino acids during protein synthesis. �� r-RNA forms the structural and catalytic component of ribosomes.

✅ Correct Answer Explanation

Messenger RNA (m-RNA) carries the genetic message from DNA to ribosomes. Transfer RNA (t-RNA) transports specific amino acids during protein synthesis. Ribosomal RNA (r-RNA) combines with proteins to form ribosomes and catalyses peptide bond formation. Therefore, the correct matching is 1-c, 2-a and 3-b, making Option A correct.

❓ Why Other Options Are Incorrect

�� Option B → All three RNA types are incorrectly matched.
�� Option C → Messenger RNA and Ribosomal RNA are interchanged.
�� Option D → Transfer RNA and Ribosomal RNA are interchanged.

🎯 Strategy

Used

Option Grouping

Application:

Match each RNA abbreviation with its full biological name.

Final Logic:

m-RNA→Messenger, t-RNA→Transfer, r-RNA→Ribosomal; therefore Option A is correct.

🧠 Memory Trick

M = Message, T = Transfer, R = Ribosome

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Types and Functions of RNA

6 Consider the secondary structure of RNA. Which statement is correct?

A It consists of a strict double-strand helix exactly like DNA.

B It is a single-stranded helix which sometimes folds back on itself.

C It never forms hydrogen bonds.

D It solely forms branched structures.

💡 Short Explanation

�� RNA is generally single-stranded. �� It can fold back because of complementary base pairing within the same strand. �� These folds help RNA perform its biological functions.

✅ Correct Answer Explanation

Unlike DNA, RNA is generally single-stranded. However, complementary bases within the same RNA molecule can pair with each other, allowing the strand to fold back and form secondary structures such as hairpin loops. These structures are important for the biological functions of RNA molecules. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → RNA is generally not a regular double helix like DNA.
�� Option C → RNA does form hydrogen bonds during secondary structure formation.
�� Option D → RNA forms several structural conformations, not only branched structures.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Compare the structural organization of RNA with that of DNA.

Final Logic:

RNA is primarily single-stranded but folds back on itself through hydrogen bonding; therefore Option B is correct.

🧠 Memory Trick

RNA = Single Strand + Self Fold

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Structure of RNA

7 Identify the specific reaction type required to break down nucleic acids completely to yield a pentose sugar, phosphoric acid, and nitrogen bases.

A Condensation

B Hydrogenation

C Complete Hydrolysis

D Esterification

💡 Short Explanation

�� Nucleic acids are polymers of nucleotides. �� Hydrolysis breaks the phosphodiester bonds between nucleotides. �� Complete hydrolysis produces pentose sugar, phosphoric acid and nitrogenous bases.

✅ Correct Answer Explanation

Nucleic acids undergo complete hydrolysis to yield their constituent components, namely pentose sugar (ribose or deoxyribose), phosphoric acid and nitrogenous bases. Hydrolysis involves breaking chemical bonds by the addition of water molecules. Therefore, Option C is correct.

❓ Why Other Options Are Incorrect

�� Option A → Condensation joins molecules by removing water rather than breaking them apart.
�� Option B → Hydrogenation involves the addition of hydrogen and is unrelated to nucleic acid breakdown.
�� Option D → Esterification forms ester bonds rather than breaking nucleic acids into their components.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Identify the reaction responsible for breaking a polymer into its monomeric components.

Final Logic:

Complete hydrolysis breaks nucleic acids into sugars, bases and phosphoric acid; therefore Option C is correct.

🧠 Memory Trick

Hydrolysis = Hydro (Water) + Lysis (Break)

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Hydrolysis of Nucleic Acids

8 The repeating unit linking the 5′ carbon of one sugar to the 3′ carbon of another in a nucleic acid is:

A Sulphate group

B Phosphodiester linkage

C Amide linkage

D Peptide bond

💡 Short Explanation

�� DNA and RNA possess a sugar-phosphate backbone. �� Adjacent nucleotides are joined through phosphodiester bonds. �� The linkage connects the 5′ phosphate of one nucleotide to the 3′ hydroxyl group of the next.

✅ Correct Answer Explanation

The nucleotides of DNA and RNA are connected by 3′–5′ phosphodiester linkages. The phosphate group attached to the 5′ carbon of one nucleotide forms an ester bond with the 3′ hydroxyl group of the adjacent pentose sugar. This repeating linkage forms the sugar-phosphate backbone of nucleic acids. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → Sulphate groups are not components of nucleic acid backbones.
�� Option C → Amide linkages occur in proteins, not nucleic acids.
�� Option D → Peptide bonds join amino acids to form proteins.

🎯 Strategy

Used

Keyword Association

Application:

Associate the terms 5′ carbon and 3′ carbon with the bond that forms the nucleic acid backbone.

Final Logic:

The sugar-phosphate backbone consists of phosphodiester linkages; therefore Option B is correct.

🧠 Memory Trick

5′ → Phosphate → 3′ = Phosphodiester

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Phosphodiester Linkage in DNA and RNA

9 The complementary base pairing in a DNA strand is strict because:

A All bases have identical molecular weights.

B Sugars inherently repel non-complementary bases.

C Covalent bonds bridge the two strands.

D Hydrogen bonds only form between specific pairs of purine and pyrimidine bases.

💡 Short Explanation

�� Complementary base pairing maintains DNA stability. �� Adenine pairs with Thymine, while Cytosine pairs with Guanine. �� These pairs form specific hydrogen bonds.

✅ Correct Answer Explanation

DNA exhibits complementary base pairing because hydrogen bonds form only between specific purine and pyrimidine bases. Adenine pairs with Thymine through two hydrogen bonds, whereas Cytosine pairs with Guanine through three hydrogen bonds. These specific interactions maintain the uniform width and stability of the DNA double helix. Therefore, Option D is correct.

❓ Why Other Options Are Incorrect

�� Option A → Complementary pairing is unrelated to molecular weight.

Option B → Sugar molecules do not determine complementary base pairing.

�� Option C → The two DNA strands are held together by hydrogen bonds, not covalent bonds.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Recall the molecular basis of Watson–Crick complementary base pairing.

Final Logic:

Specific hydrogen bonding between complementary bases ensures accurate pairing; therefore Option B is correct.

🧠 Memory Trick

AT = 2, CG = 3

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Complementary Base Pairing in DNA

10 Consider the following statements about nitrogen bases:
1. DNA and RNA contain the exact same pyrimidines.
2. Uracil replaces thymine in RNA.
3. Adenine forms hydrogen bonds with thymine in DNA.

A 1 and 2

B 2 and 3

C 1 and 3

D 1, 2 and 3

💡 Short Explanation

�� DNA contains Thymine, whereas RNA contains Uracil. �� Adenine pairs with Thymine in DNA. �� Therefore, DNA and RNA do not possess identical pyrimidines.

✅ Correct Answer Explanation

Statement 1 is incorrect because DNA contains the pyrimidines Cytosine and Thymine, whereas RNA contains Cytosine and Uracil. Statement 2 is correct because Uracil replaces Thymine in RNA. Statement 3 is correct because Adenine forms two hydrogen bonds with Thymine in DNA. Therefore, the correct combination is Statements 2 and 3, making Option B correct.

❓ Why Other Options Are Incorrect

�� Option A → Includes incorrect statement 1.
�� Option C → Includes incorrect statement 1 and omits correct statement 2.
�� Option D → Includes incorrect statement 1.

🎯 Strategy

Used

Elimination

Application:

Identify the incorrect statement first and eliminate all options containing it.

Final Logic:

Statement 1 is incorrect, whereas 2 and 3 are correct; therefore Option B is correct.

🧠 Memory Trick

DNA = T | RNA = U | A ↔ T

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Nitrogenous Bases of DNA and RNA

11 Which fundamental unit is missing from a nucleoside to prevent it from becoming a nucleotide?

A A pentose sugar

B A nitrogenous base

C A phosphoric acid moiety

D A hydroxyl group

💡 Short Explanation

�� A nucleoside consists of a pentose sugar and a nitrogenous base. �� A nucleotide contains an additional phosphate group. �� Therefore, the missing component is phosphoric acid.

✅ Correct Answer Explanation

A nucleoside is composed of a pentose sugar and a nitrogenous base. When a phosphoric acid (phosphate) group is attached to the nucleoside, it forms a nucleotide, which is the monomer of nucleic acids. Therefore, the component absent in a nucleoside is the phosphoric acid moiety, making Option C correct.

❓ Why Other Options Are Incorrect

�� Option A → A pentose sugar is already present in a nucleoside.
�� Option B → A nitrogenous base is also an essential component of a nucleoside.
�� Option D → Hydroxyl groups are naturally present on the pentose sugar and are not the distinguishing component between a nucleoside and a nucleotide.

🎯 Strategy

Used

Conceptual Reasoning

Application:

Compare the structural composition of a nucleoside and a nucleotide.

Final Logic:

Nucleoside + Phosphate = Nucleotide; therefore Option C is correct.

🧠 Memory Trick

Sugar + Base + Phosphate = Nucleotide

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Nucleosides and Nucleotides

12 Arrange the structural formation steps of a polynucleotide in the correct chronological sequence:
(A) Formation of phosphodiester linkage
(B) Attachment of base to 1' position of sugar
(C) Linkage to phosphoric acid at 5' position
(D) Winding into a double helix

A (A), (B), (C), (D)

B (B), (C), (A), (D)

C (C), (B), (D), (A)

D (B), (A), (C), (D)

💡 Short Explanation

�� The nitrogenous base first joins the pentose sugar. �� The phosphate group then forms a nucleotide. �� Nucleotides polymerize before the DNA double helix is formed.

✅ Correct Answer Explanation

The sequence begins with the attachment of the nitrogenous base to the 1′ carbon of the pentose sugar, producing a nucleoside. Next, phosphoric acid attaches to the 5′ carbon, producing a nucleotide. Adjacent nucleotides are then joined by phosphodiester linkages to form a polynucleotide chain. Finally, in DNA, two complementary polynucleotide chains wind around each other to form the double helix. Therefore, the correct sequence is B → C → A → D, making Option B correct.

❓ Why Other Options Are Incorrect

�� Option A → Begins with phosphodiester linkage before nucleotide formation.
�� Option C → Phosphate cannot attach before the nitrogenous base forms the nucleoside.
�� Option D → Phosphodiester linkage cannot form before nucleotide formation is complete.

🎯 Strategy

Used

Ordering

Application:

Arrange the molecular events from nucleoside formation to DNA structure.

Final Logic:

Base → Phosphate → Phosphodiester Bond → Double Helix; therefore Option B is correct.

🧠 Memory Trick

Base → Phosphate → Backbone → Helix

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Formation of Polynucleotides

13 In the structural formation of a nucleotide, which numeric carbon position serves as the attachment point for the phosphoric acid?

A 1′

B 2′

C 3′

D 5′

💡 Short Explanation

�� The phosphate group is attached to the pentose sugar. �� It joins specifically at the 5′ carbon atom. �� This phosphate later participates in phosphodiester bond formation.

✅ Correct Answer Explanation

A nucleotide is formed when phosphoric acid is attached to the 5′ carbon atom of the pentose sugar present in a nucleoside. During nucleic acid synthesis, this phosphate group participates in forming 3′–5′ phosphodiester linkages, connecting adjacent nucleotides into DNA and RNA chains. Therefore, Option D is correct.

❓ Why Other Options Are Incorrect

�� Option A → The 1′ carbon is attached to the nitrogenous base through an N-glycosidic bond.
�� Option B → The 2′ carbon is not the attachment site for phosphate in standard nucleotides.
�� Option C → The 3′ carbon participates in phosphodiester linkage formation but is not the site where phosphate is initially attached.

🎯 Strategy

Used

Direct Recall

Application:

Recall the position of phosphate attachment during nucleotide formation.

Final Logic:

The phosphate group attaches at the 5′ carbon of the pentose sugar; therefore Option D is correct.

🧠 Memory Trick

5′ = Phosphate Point

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Structure of Nucleotides

14 Match the bond type (List-I) with its corresponding biological role in nucleic acids (List-II)

List I	List II
1. — Phosphodiester linkage	a. — Holds the two complementary DNA strands together
2. — Hydrogen bond	b. — Joins the base to the 1′ position of the sugar
3. — N-Glycosidic linkage (Base to sugar)	c. — Joins the 5′ and 3′ carbons of adjacent sugars

A (1)-(c), (2)-(a), (3)-(b)

B (1)-(a), (2)-(c), (3)-(b)

C (1)-(b), (2)-(a), (3)-(c)

D (1)-(c), (2)-(b), (3)-(a)

💡 Short Explanation

�� Phosphodiester linkage forms the sugar-phosphate backbone. �� Hydrogen bonds hold complementary DNA strands together. �� N-Glycosidic linkage joins the nitrogenous base to the sugar.

✅ Correct Answer Explanation

The phosphodiester linkage joins the 5′ phosphate group of one nucleotide to the 3′ hydroxyl group of the next sugar, forming the backbone of DNA and RNA. Hydrogen bonds hold complementary nitrogenous bases together between the two DNA strands. The N-glycosidic linkage joins the nitrogenous base to the 1′ carbon of the pentose sugar, forming a nucleoside. Therefore, the correct matching is 1-c, 2-a and 3-b, making Option A correct.

❓ Why Other Options Are Incorrect

�� Option B → Phosphodiester linkage does not hold DNA strands together, and hydrogen bonds do not join adjacent sugars.
�� Option C → Phosphodiester linkage is incorrectly matched with base-sugar linkage.
�� Option D → Hydrogen bonds do not join the base to the sugar, and N-glycosidic linkage does not hold DNA strands together.

🎯 Strategy

Used

Option Grouping

Application:

Match each bond with its unique structural function in nucleic acids.

Final Logic:

Phosphodiester→Backbone, Hydrogen bond→Complementary strands, N-Glycosidic→Base to sugar; therefore Option A is correct.

🧠 Memory Trick

P–Backbone | H–Helix | N–Base

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Bonds Present in Nucleic Acids

15 Which components constitute the "rails" or backbone of the twisted ladder structure in the DNA double helix?

A Pairs of purine and pyrimidine bases

B Alternating units of phosphate and deoxyribose sugar

C Adjacent nitrogenous bases

D Ribose and uracil units

💡 Short Explanation

�� DNA resembles a twisted ladder. �� The backbone forms the rails of the ladder. �� It consists of alternating deoxyribose sugar and phosphate groups.

✅ Correct Answer Explanation

In the DNA double helix, the rails (backbone) are formed by alternating deoxyribose sugar and phosphate groups, connected through phosphodiester linkages. The nitrogenous bases project inward and form the rungs of the ladder. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → Base pairs form the rungs, not the rails.
�� Option C → Nitrogenous bases alone do not constitute the backbone.
�� Option D → Ribose and uracil are components of RNA, not DNA.

🎯 Strategy

Used

Structural Visualization

Application:

Visualize the DNA double helix as a twisted ladder.

Final Logic:

Sugar-phosphate units form the rails; therefore Option B is correct.

🧠 Memory Trick

Backbone = Sugar + Phosphate

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Structure of DNA Double Helix

16 The specific architectural feature that acts as the "rungs" of the DNA ladder is:

A Alternating phosphate units

B Deoxyribose sugars

C A pair of purine/pyrimidine bases

D Phosphodiester linkages

💡 Short Explanation

�� DNA resembles a twisted ladder. �� The base pairs form the rungs. �� Complementary purine and pyrimidine bases are held together by hydrogen bonds.

✅ Correct Answer Explanation

The rungs of the DNA ladder are formed by complementary nitrogenous base pairs, where a purine pairs with a pyrimidine. Adenine pairs with Thymine through two hydrogen bonds, while Cytosine pairs with Guanine through three hydrogen bonds. These paired bases stabilize the DNA double helix. Therefore, Option C is correct.

❓ Why Other Options Are Incorrect

�� Option A → Phosphate groups are part of the backbone, not the rungs.
�� Option B → Deoxyribose sugars form the backbone along with phosphate groups.
�� Option D → Phosphodiester linkages connect adjacent nucleotides in the backbone and do not form the rungs.

🎯 Strategy

Used

Structural Visualization

Application:

Identify the parts of the DNA ladder by comparing its structure to a physical ladder.

Final Logic:

Complementary base pairs form the rungs, whereas the sugar-phosphate backbone forms the rails; therefore Option C is correct.

🧠 Memory Trick

Rails = Sugar–Phosphate | Rungs = Base Pairs

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: DNA Double Helix and Complementary Base Pairing

17 Regarding the process of DNA fingerprinting:

A The sequence of bases can be easily altered by medical surgery.

B It relies on the fact that a sequence of bases on DNA is unique for a person.

C It is identical across all members of a specific racial group.

D It utilizes RNA molecules from the bloodstream.

💡 Short Explanation

�� Every individual has a unique DNA sequence (except identical twins). �� This uniqueness forms the basis of DNA fingerprinting. �� DNA fingerprinting is widely used in forensic science and paternity testing.

✅ Correct Answer Explanation

DNA fingerprinting is based on the principle that the sequence of bases and certain DNA regions are unique for every individual (except identical twins). This uniqueness allows forensic scientists to identify individuals accurately using DNA samples collected from crime scenes or biological specimens. Therefore, Option B is correct.

❓ Why Other Options Are Incorrect

�� Option A → Medical surgery cannot alter an individual's DNA sequence used for fingerprinting.
�� Option C → DNA sequences differ among individuals and are not identical within a racial group.
�� Option D → DNA fingerprinting analyzes DNA, not RNA, obtained from biological samples.

🎯 Strategy

Used

Keyword Association

Application:

Associate the term DNA fingerprinting with unique DNA sequence.

Final Logic:

DNA fingerprinting depends on the uniqueness of an individual's DNA; therefore Option B is correct.

🧠 Memory Trick

Unique DNA = Unique Identity

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: DNA Fingerprinting

18 Which statement accurately describes the division of labor between nucleic acids in protein synthesis?

A 1. DNA performs the synthesis, while RNA stores the message.

B 2. Both DNA and RNA equally synthesize proteins independently.

C . DNA has the coded 3message, while RNA molecules actually carry out the synthesis.

D 4. RNA relies on DNA to leave the nucleus and build proteins.

💡 Short Explanation

DNA stores genetic information.
RNA transfers and translates this information into proteins.
mRNA, tRNA and rRNA work together during protein synthesis.

✅ Correct Answer Explanation

DNA serves as the repository of genetic information by storing the coded instructions for protein synthesis. During gene expression, this information is transferred to messenger RNA (mRNA). Along with transfer RNA (tRNA) and ribosomal RNA (rRNA), RNA molecules participate directly in translating the genetic code into proteins. Thus, DNA stores the message, whereas RNA carries out protein synthesis. Therefore, Option C is correct.

❓ Why Other Options Are Incorrect

Option 1 → DNA stores the genetic message but does not directly synthesize proteins.
Option 2 → DNA and RNA do not independently perform the same function. Their roles are different and complementary.
Option 4 → RNA does not depend on DNA leaving the nucleus; DNA generally remains in the nucleus, while RNA carries the genetic message to ribosomes.

🎯 Strategy

Conceptual Reasoning

Application:

Differentiate the functions of DNA and the various RNA molecules during protein synthesis.

Final Logic:

DNA stores the genetic code, whereas RNA executes protein synthesis; therefore Option C is correct.

5. Memory Trick

🧠 Memory Trick

DNA Directs → RNA Reads → Protein Results

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Functions of DNA and RNA in Protein Synthesis

📄 Passage

The role of insulin in keeping the blood glucose level within the narrow limit is an example of this function. Insulin is released in response to the rapid rise in blood glucose level. On the other hand, hormone glucagon tends to increase the glucose level in the blood. The two hormones together regulate the glucose level in the blood. Epinephrine and norepinephrine mediate responses to external stimuli. Growth hormones and sex hormones play a role in growth and development. Thyroxine produced in the thyroid gland is an iodinated derivative of the amino acid tyrosine.

Based on the passage, identify the correct reaction/functional relationship between insulin and glucagon.

A Both continuously increase blood glucose levels.

B Insulin increases glucose levels, while glucagon decreases them.

C Insulin is released due to rising glucose, while glucagon tends to increase it, working together to regulate levels.

D Both strictly inhibit the absorption of glucose by cells.

💡 Short Explanation

�� Insulin is released when blood glucose rises. �� Glucagon increases blood glucose levels. �� Together, they maintain blood glucose homeostasis.

✅ Correct Answer Explanation

According to the passage, insulin is secreted in response to an increase in blood glucose concentration and helps lower it toward the normal range. Glucagon, on the other hand, tends to increase blood glucose levels when they fall. These hormones act in a complementary manner to maintain blood glucose within a narrow physiological range. Therefore, Option C is correct.

❓ Why Other Options Are Incorrect

�� Option A → Only glucagon increases blood glucose; insulin lowers it.
�� Option B → The functions of insulin and glucagon are reversed.
�� Option D → The passage does not state that both hormones inhibit glucose absorption; instead, they regulate blood glucose concentration.

🎯 Strategy

Used

Contextual/Tonal Matching

Application:

Identify the relationship between insulin and glucagon as described in the passage.

Final Logic:

Insulin lowers blood glucose after it rises, while glucagon raises it when required; together they regulate blood glucose. Therefore, Option C is correct.

🧠 Memory Trick

GLUCAgon → GLUCose Goes Up

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Hormones – Functions of Insulin and Glucagon

20 The role of insulin in keeping the blood glucose level within the narrow limit is an example of this function. Insulin is released in response to the rapid rise in blood glucose level. On the other hand, hormone glucagon tends to increase the glucose level in the blood. The two hormones together regulate the glucose level in the blood. Epinephrine and norepinephrine mediate responses to external stimuli. Growth hormones and sex hormones play a role in growth and development. Thyroxine produced in the thyroid gland is an iodinated derivative of the amino acid tyrosine.
Based on the passage, the naming classification of thyroxine identifies it fundamentally as a derivative of which unit?

A A steroid molecule

B A polypeptide chain

C A complex carbohydrate

D The amino acid tyrosine

💡 Short Explanation

�� Thyroxine is produced by the thyroid gland. �� It is an iodinated derivative of the amino acid tyrosine. �� It is neither a steroid nor a polypeptide hormone.

✅ Correct Answer Explanation

The passage clearly states that thyroxine is an iodinated derivative of the amino acid tyrosine. This classifies thyroxine as an amino acid-derived hormone rather than a steroid or peptide hormone. Therefore, Option D is correct.

❓ Why Other Options Are Incorrect

�� Option A → Thyroxine is not a steroid hormone. Steroid hormones include estrogens and androgens.
�� Option B → Thyroxine is not a polypeptide hormone like insulin.
�� Option C → Thyroxine is unrelated to carbohydrates.

🎯 Strategy

Used

Contextual/Tonal Matching

Application:

Locate the classification of thyroxine directly from the passage.

Final Logic:

The passage identifies thyroxine as an iodinated derivative of tyrosine; therefore Option C is correct.

🧠 Memory Trick

(Both begin with "TY", making the association easy to remember.)

📚 Class XII – Chemistry – Chapter: Biomolecules – Topic: Hormones – Chemical Nature of Thyroxine

CUET UG Chemistry Booster Test – 2 Nucleic Acids and Hormones

CUET UG Chemistry Booster Test - 1 Nucleic Acids and Hormones

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