Genetics & Molecular Biology explores how genetic information is inherited, expressed, and regulated at the molecular level. This category integrates classical genetics with modern molecular biology to explain the mechanisms governing heredity, variation, and gene expression , making it suitable for Class 11–12 students , NEET aspirants , and undergraduate learners .
In this section, you will study:
Basic concepts of genetics and heredity
Mendelian and non-Mendelian inheritance patterns
Molecular structure of DNA and RNA
DNA replication, transcription, and translation
Gene regulation and expression
Mutations and genetic disorders
Recombinant DNA technology and molecular tools
NCERT-based explanations, diagrams, MCQs, and exam-oriented questions
The content is structured to build strong conceptual foundations , improve problem-solving and analytical skills , and help students perform confidently in school examinations, NEET, and undergraduate assessments .
Develop a clear and integrated understanding of genetics and molecular biology to master one of the most important and scoring areas of modern Biology.
Q. What type of RNA is primarily involved in the regulation of gene expression through RNA interference?
A.
mRNA
B.
tRNA
C.
rRNA
D.
siRNA
Show solution
Solution
siRNA (small interfering RNA) plays a crucial role in RNA interference, regulating gene expression by degrading mRNA.
Correct Answer:
D
— siRNA
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Q. Which base is found in RNA but not in DNA?
A.
Thymine
B.
Uracil
C.
Cytosine
D.
Adenine
Show solution
Solution
RNA contains uracil instead of thymine, which is found in DNA.
Correct Answer:
B
— Uracil
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Q. Which base is NOT found in RNA?
A.
Adenine
B.
Cytosine
C.
Thymine
D.
Uracil
Show solution
Solution
Thymine is not found in RNA; it is replaced by uracil.
Correct Answer:
C
— Thymine
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Q. Which enzyme is essential for synthesizing new DNA strands during PCR?
A.
DNA ligase
B.
Taq polymerase
C.
Reverse transcriptase
D.
Restriction enzyme
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Solution
Taq polymerase is a heat-stable enzyme that synthesizes new DNA strands during the PCR process.
Correct Answer:
B
— Taq polymerase
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Q. Which enzyme is essential for the PCR process?
A.
DNA ligase
B.
Taq polymerase
C.
Reverse transcriptase
D.
Restriction enzyme
Show solution
Solution
Taq polymerase is a heat-stable enzyme that synthesizes new DNA strands during the PCR process.
Correct Answer:
B
— Taq polymerase
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Q. Which enzyme is primarily responsible for synthesizing new DNA strands during PCR?
A.
DNA ligase
B.
Taq polymerase
C.
Restriction enzyme
D.
RNA polymerase
Show solution
Solution
Taq polymerase is a heat-stable enzyme that synthesizes new DNA strands during the PCR process.
Correct Answer:
B
— Taq polymerase
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Q. Which enzyme is responsible for synthesizing RNA during transcription?
A.
DNA polymerase
B.
RNA polymerase
C.
Ribosome
D.
Ligase
Show solution
Solution
RNA polymerase is the enzyme that synthesizes RNA by transcribing the DNA template during transcription.
Correct Answer:
B
— RNA polymerase
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Q. Which molecular technique is used to amplify DNA?
A.
Gel electrophoresis
B.
PCR
C.
Cloning
D.
Sequencing
Show solution
Solution
Polymerase Chain Reaction (PCR) is the technique used to amplify specific DNA sequences, making millions of copies of a target DNA segment.
Correct Answer:
B
— PCR
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Q. Which molecular technique is used to separate DNA fragments by size?
A.
Gel electrophoresis
B.
PCR
C.
Cloning
D.
DNA sequencing
Show solution
Solution
Gel electrophoresis is used to separate DNA fragments based on their size, allowing for analysis and comparison.
Correct Answer:
A
— Gel electrophoresis
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Q. Which mutation can result in a premature stop codon?
A.
Silent mutation
B.
Missense mutation
C.
Nonsense mutation
D.
Frameshift mutation
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Solution
A nonsense mutation can result in a premature stop codon, leading to truncated proteins.
Correct Answer:
C
— Nonsense mutation
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Q. Which mutation results in a change in a single amino acid in a protein?
A.
Silent mutation
B.
Nonsense mutation
C.
Missense mutation
D.
Frameshift mutation
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Solution
A missense mutation is a type of mutation that results in the substitution of one amino acid for another in a protein.
Correct Answer:
C
— Missense mutation
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Q. Which nitrogenous base is found in RNA but not in DNA?
A.
Thymine
B.
Uracil
C.
Cytosine
D.
Adenine
Show solution
Solution
Uracil is a nitrogenous base found in RNA, replacing thymine which is present in DNA.
Correct Answer:
B
— Uracil
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Q. Which of the following bases is found in RNA but not in DNA?
A.
Thymine
B.
Uracil
C.
Cytosine
D.
Adenine
Show solution
Solution
RNA contains uracil instead of thymine, which is found in DNA.
Correct Answer:
B
— Uracil
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Q. Which of the following best describes a frameshift mutation?
A.
A mutation that changes one amino acid
B.
A mutation that adds or removes nucleotides, altering the reading frame
C.
A mutation that duplicates a segment of DNA
D.
A mutation that occurs in non-coding regions
Show solution
Solution
A frameshift mutation occurs when nucleotides are added or removed from the DNA sequence, shifting the reading frame and altering the resulting protein.
Correct Answer:
B
— A mutation that adds or removes nucleotides, altering the reading frame
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Q. Which of the following best describes a test cross?
A.
Crossing two homozygous individuals
B.
Crossing a homozygous individual with a heterozygous individual
C.
Crossing an individual with an unknown genotype with a homozygous recessive
D.
Crossing two heterozygous individuals
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Solution
A test cross involves crossing an individual with an unknown genotype with a homozygous recessive individual to determine the genotype of the former.
Correct Answer:
C
— Crossing an individual with an unknown genotype with a homozygous recessive
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Q. Which of the following best describes the process of translation?
A.
DNA is copied into RNA
B.
RNA is converted into a protein
C.
Proteins are degraded
D.
RNA is replicated
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Solution
Translation is the process where the sequence of nucleotides in mRNA is translated into a sequence of amino acids, forming a protein.
Correct Answer:
B
— RNA is converted into a protein
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Q. Which of the following describes a mutation?
A.
A change in the DNA sequence
B.
A process of DNA replication
C.
A type of RNA molecule
D.
A form of genetic inheritance
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Solution
A mutation is defined as a change in the DNA sequence that can lead to alterations in gene function.
Correct Answer:
A
— A change in the DNA sequence
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Q. Which of the following describes a phenotype?
A.
The genetic makeup of an organism
B.
The observable characteristics of an organism
C.
The location of a gene on a chromosome
D.
The sequence of nucleotides in DNA
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Solution
A phenotype refers to the observable characteristics or traits of an organism, which result from the interaction of its genotype with the environment.
Correct Answer:
B
— The observable characteristics of an organism
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Q. Which of the following describes the structure of DNA?
A.
Single-stranded helix
B.
Double-stranded helix
C.
Triple-stranded helix
D.
Linear structure
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Solution
DNA is structured as a double-stranded helix, with two strands running antiparallel.
Correct Answer:
B
— Double-stranded helix
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Q. Which of the following is a characteristic of a recessive trait?
A.
Expressed in homozygous individuals only
B.
Expressed in heterozygous individuals
C.
Always expressed
D.
Dominates over other traits
Show solution
Solution
A recessive trait is expressed only in homozygous individuals, meaning both alleles must be recessive.
Correct Answer:
A
— Expressed in homozygous individuals only
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Q. Which of the following is a characteristic of autosomal dominant inheritance?
A.
Trait skips generations
B.
Both males and females are equally affected
C.
Affected individuals are always homozygous
D.
Only males can transmit the trait
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Solution
In autosomal dominant inheritance, both males and females are equally affected, and the trait does not skip generations.
Correct Answer:
B
— Both males and females are equally affected
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Q. Which of the following is a characteristic of DNA?
A.
Single-stranded
B.
Contains ribose sugar
C.
Double helix structure
D.
Contains uracil
Show solution
Solution
DNA is characterized by its double helix structure, consisting of two strands wound around each other.
Correct Answer:
C
— Double helix structure
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Q. Which of the following is a characteristic of Mendelian inheritance?
A.
Traits are influenced by multiple genes
B.
Traits segregate independently
C.
All traits are dominant
D.
Only recessive traits are expressed
Show solution
Solution
Mendelian inheritance is characterized by the independent segregation of traits, as described in Mendel's laws.
Correct Answer:
B
— Traits segregate independently
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Q. Which of the following is a characteristic of recessive alleles?
A.
Always expressed in the phenotype
B.
Only expressed in homozygous condition
C.
Expressed in heterozygous condition
D.
Dominates over all other alleles
Show solution
Solution
Recessive alleles are only expressed in the phenotype when in a homozygous condition (two copies of the recessive allele).
Correct Answer:
B
— Only expressed in homozygous condition
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Q. Which of the following is a characteristic of RNA compared to DNA?
A.
Double-stranded structure
B.
Deoxyribose sugar
C.
Single-stranded structure
D.
Thymine base
Show solution
Solution
RNA is typically single-stranded, while DNA is double-stranded.
Correct Answer:
C
— Single-stranded structure
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Q. Which of the following is a characteristic of RNA?
A.
Double-stranded structure
B.
Contains deoxyribose
C.
Single-stranded structure
D.
Contains thymine
Show solution
Solution
RNA is typically single-stranded and contains ribose sugar.
Correct Answer:
C
— Single-stranded structure
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Q. Which of the following is a characteristic of the double helix structure of DNA?
A.
Antiparallel strands
B.
Single-stranded
C.
Left-handed twist
D.
No hydrogen bonds
Show solution
Solution
The double helix structure of DNA features two antiparallel strands that are held together by hydrogen bonds between complementary bases.
Correct Answer:
A
— Antiparallel strands
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Q. Which of the following is a common application of cloning in biotechnology?
A.
Gene therapy
B.
DNA sequencing
C.
Protein purification
D.
All of the above
Show solution
Solution
Cloning is used in various applications, including gene therapy, DNA sequencing, and protein purification.
Correct Answer:
D
— All of the above
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Q. Which of the following is a common application of PCR?
A.
Gene therapy
B.
Forensic analysis
C.
Protein purification
D.
Cell culture
Show solution
Solution
PCR is widely used in forensic analysis to amplify DNA from crime scene samples for identification.
Correct Answer:
B
— Forensic analysis
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Q. Which of the following is a component of RNA but not DNA?
A.
Thymine
B.
Uracil
C.
Deoxyribose
D.
Adenine
Show solution
Solution
RNA contains uracil instead of thymine, which is found in DNA.
Correct Answer:
B
— Uracil
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