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 is the role of ribosomes in protein synthesis?
A.
To transcribe DNA into RNA
B.
To translate mRNA into polypeptides
C.
To replicate DNA
D.
To splice introns from mRNA
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Solution
Ribosomes are the cellular machinery that translates mRNA into polypeptides, facilitating protein synthesis.
Correct Answer:
B
— To translate mRNA into polypeptides
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Q. What is the role of RNA polymerase in gene expression?
A.
To replicate DNA
B.
To synthesize RNA from a DNA template
C.
To splice RNA
D.
To translate RNA into protein
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Solution
RNA polymerase synthesizes RNA from a DNA template during the process of transcription in gene expression.
Correct Answer:
B
— To synthesize RNA from a DNA template
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Q. What is the role of the 5' cap in mRNA processing?
A.
To signal the start of translation
B.
To protect mRNA from degradation
C.
To facilitate splicing
D.
To enhance transcription
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Solution
The 5' cap protects mRNA from degradation and assists in the initiation of translation by helping ribosomes recognize the mRNA.
Correct Answer:
B
— To protect mRNA from degradation
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Q. What is the role of the promoter in gene expression?
A.
To terminate transcription
B.
To enhance translation
C.
To initiate transcription
D.
To splice RNA
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Solution
The promoter is a DNA sequence that initiates transcription by providing a binding site for RNA polymerase.
Correct Answer:
C
— To initiate transcription
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Q. What is the role of tRNA during translation?
A.
To carry amino acids to the ribosome
B.
To synthesize mRNA
C.
To unwind DNA
D.
To form peptide bonds
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Solution
tRNA (transfer RNA) carries specific amino acids to the ribosome, where they are added to the growing polypeptide chain during translation.
Correct Answer:
A
— To carry amino acids to the ribosome
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Q. What is the role of tRNA in translation?
A.
To carry amino acids to the ribosome
B.
To synthesize mRNA
C.
To replicate DNA
D.
To form ribosomal subunits
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Solution
tRNA (transfer RNA) carries specific amino acids to the ribosome during translation, matching them to the codons on the mRNA.
Correct Answer:
A
— To carry amino acids to the ribosome
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Q. What is the significance of gel electrophoresis in molecular biology?
A.
To separate DNA fragments based on size
B.
To amplify DNA
C.
To synthesize proteins
D.
To sequence RNA
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Solution
Gel electrophoresis is used to separate DNA fragments based on their size, allowing for analysis and comparison.
Correct Answer:
A
— To separate DNA fragments based on size
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Q. What is the significance of the 'denaturation' step in PCR?
A.
To cool the reaction mixture
B.
To separate the DNA strands
C.
To synthesize new DNA strands
D.
To add primers
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Solution
Denaturation involves heating the reaction mixture to separate the double-stranded DNA into single strands.
Correct Answer:
B
— To separate the DNA strands
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Q. What is the significance of the 'sticky ends' created by restriction enzymes?
A.
They stabilize RNA
B.
They allow for the easy joining of DNA fragments
C.
They prevent mutations
D.
They enhance PCR efficiency
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Solution
'Sticky ends' are overhanging sequences that facilitate the ligation of DNA fragments during cloning.
Correct Answer:
B
— They allow for the easy joining of DNA fragments
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Q. What is the significance of the 'sticky ends' in DNA cloning?
A.
They prevent DNA degradation
B.
They facilitate the ligation of DNA fragments
C.
They enhance PCR efficiency
D.
They stabilize RNA structures
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Solution
'Sticky ends' are overhanging sequences that allow for the easy joining of DNA fragments during cloning.
Correct Answer:
B
— They facilitate the ligation of DNA fragments
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Q. What is the significance of the 'sticky ends' in recombinant DNA technology?
A.
They help in DNA replication
B.
They facilitate the ligation of DNA fragments
C.
They are used for PCR amplification
D.
They stabilize the DNA structure
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Solution
'Sticky ends' are overhanging sequences that allow for the easy ligation of DNA fragments during recombinant DNA technology.
Correct Answer:
B
— They facilitate the ligation of DNA fragments
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Q. What is the significance of the 'sticky ends' produced by some restriction enzymes?
A.
They allow for easier ligation of DNA fragments
B.
They prevent DNA degradation
C.
They enhance PCR efficiency
D.
They facilitate RNA transcription
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Solution
'Sticky ends' created by certain restriction enzymes allow for easier ligation of DNA fragments by providing complementary overhangs.
Correct Answer:
A
— They allow for easier ligation of DNA fragments
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Q. What is the significance of the 5' and 3' ends of a DNA strand?
A.
They indicate the direction of replication
B.
They determine the type of base pairs
C.
They are sites for protein binding
D.
They are involved in RNA splicing
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Solution
The 5' and 3' ends of a DNA strand indicate the direction of replication and transcription, as nucleic acids are synthesized in the 5' to 3' direction.
Correct Answer:
A
— They indicate the direction of replication
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Q. What is the significance of the 5' cap and poly-A tail in eukaryotic mRNA?
A.
They are involved in DNA replication
B.
They protect mRNA from degradation and assist in translation
C.
They are sites for transcription initiation
D.
They help in splicing introns
Show solution
Solution
The 5' cap and poly-A tail protect mRNA from degradation and facilitate its recognition and translation by ribosomes.
Correct Answer:
B
— They protect mRNA from degradation and assist in translation
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Q. What is the significance of the 5' cap and poly-A tail in mRNA?
A.
They are involved in DNA replication
B.
They protect mRNA from degradation and assist in translation
C.
They are required for transcription initiation
D.
They help in the splicing of introns
Show solution
Solution
The 5' cap and poly-A tail protect mRNA from degradation and facilitate its translation by ribosomes.
Correct Answer:
B
— They protect mRNA from degradation and assist in translation
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Q. What is the significance of the promoter region in a gene?
A.
It codes for the protein
B.
It is where RNA polymerase binds to initiate transcription
C.
It terminates transcription
D.
It is a coding sequence
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Solution
The promoter region is a specific sequence of DNA where RNA polymerase binds to initiate the transcription of a gene.
Correct Answer:
B
— It is where RNA polymerase binds to initiate transcription
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Q. What is the significance of the promoter region in gene expression?
A.
It is where RNA polymerase binds to initiate transcription
B.
It codes for the protein product
C.
It is involved in splicing of mRNA
D.
It terminates transcription
Show solution
Solution
The promoter region is crucial for the initiation of transcription as it is the site where RNA polymerase binds to start synthesizing RNA.
Correct Answer:
A
— It is where RNA polymerase binds to initiate transcription
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Q. What is the significance of the start codon in mRNA?
A.
It signals the end of translation
B.
It initiates the process of translation
C.
It is the site of transcription
D.
It codes for a stop signal
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Solution
The start codon (AUG) signals the beginning of translation, indicating where the ribosome should start synthesizing the protein.
Correct Answer:
B
— It initiates the process of translation
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Q. What is the term for an observable characteristic of an organism?
A.
Genotype
B.
Phenotype
C.
Allele
D.
Locus
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Solution
Phenotype refers to the observable characteristics or traits of an organism.
Correct Answer:
B
— Phenotype
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Q. What is the term for an observable characteristic that is influenced by both genetic and environmental factors?
A.
Genotype
B.
Phenotype
C.
Allele
D.
Locus
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Solution
The term for an observable characteristic influenced by both genetic and environmental factors is phenotype.
Correct Answer:
B
— Phenotype
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Q. What is the term for different forms of a gene?
A.
Chromosomes
B.
Alleles
C.
Genotypes
D.
Phenotypes
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Solution
Alleles are different forms of a gene that can exist at a specific locus on a chromosome.
Correct Answer:
B
— Alleles
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Q. What term describes an organism's genetic makeup?
A.
Phenotype
B.
Genotype
C.
Allele
D.
Locus
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Solution
Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable traits.
Correct Answer:
B
— Genotype
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Q. What type of bond connects the sugar and phosphate groups in a DNA strand?
A.
Hydrogen bond
B.
Ionic bond
C.
Covalent bond
D.
Peptide bond
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Solution
Covalent bonds connect the sugar and phosphate groups, forming the backbone of the DNA strand.
Correct Answer:
C
— Covalent bond
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Q. What type of bond connects the sugar and phosphate groups in the DNA backbone?
A.
Hydrogen bond
B.
Ionic bond
C.
Covalent bond
D.
Peptide bond
Show solution
Solution
Covalent bonds connect the sugar and phosphate groups in the DNA backbone, providing structural stability.
Correct Answer:
C
— Covalent bond
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Q. What type of bond holds the two strands of DNA together?
A.
Ionic bonds
B.
Covalent bonds
C.
Hydrogen bonds
D.
Peptide bonds
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Solution
Hydrogen bonds between complementary nitrogenous bases hold the two strands of DNA together.
Correct Answer:
C
— Hydrogen bonds
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Q. What type of inheritance pattern is shown by a trait that skips generations?
A.
Autosomal dominant
B.
Autosomal recessive
C.
X-linked dominant
D.
X-linked recessive
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Solution
Autosomal recessive traits can skip generations because an individual must inherit two copies of the recessive allele to express the trait.
Correct Answer:
B
— Autosomal recessive
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Q. What type of mutation involves a change in a single nucleotide base pair?
A.
Frameshift mutation
B.
Point mutation
C.
Deletion mutation
D.
Insertion mutation
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Solution
A point mutation involves a change in a single nucleotide base pair, which can affect protein synthesis.
Correct Answer:
B
— Point mutation
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Q. What type of mutation involves a change in a single nucleotide?
A.
Frameshift mutation
B.
Point mutation
C.
Deletion mutation
D.
Duplication mutation
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Solution
A point mutation is a change in a single nucleotide in the DNA sequence.
Correct Answer:
B
— Point mutation
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Q. What type of mutation results in a change in a single nucleotide?
A.
Frameshift mutation
B.
Point mutation
C.
Deletion mutation
D.
Insertion mutation
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Solution
A point mutation is a change in a single nucleotide in the DNA sequence.
Correct Answer:
B
— Point mutation
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Q. What type of mutation results in a premature stop codon?
A.
Missense mutation
B.
Nonsense mutation
C.
Silent mutation
D.
Frameshift mutation
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Solution
A nonsense mutation introduces a premature stop codon, leading to truncated proteins.
Correct Answer:
B
— Nonsense mutation
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