Genetics & Molecular Biology for Competitive Exams

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Genetics & Molecular Biology

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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.

Biotechnology Applications: PCR, Cloning, Recombinant DNA Biotechnology Applications: PCR, Cloning, Recombinant DNA - Advanced Concepts Biotechnology Applications: PCR, Cloning, Recombinant DNA - Applications Biotechnology Applications: PCR, Cloning, Recombinant DNA - Case Studies Biotechnology Applications: PCR, Cloning, Recombinant DNA - Competitive Exam Level Biotechnology Applications: PCR, Cloning, Recombinant DNA - Higher Difficulty Problems Biotechnology Applications: PCR, Cloning, Recombinant DNA - Numerical Applications Biotechnology Applications: PCR, Cloning, Recombinant DNA - Problem Set Biotechnology Applications: PCR, Cloning, Recombinant DNA - Real World Applications Central Dogma: Transcription & Translation Central Dogma: Transcription & Translation - Advanced Concepts Central Dogma: Transcription & Translation - Applications Central Dogma: Transcription & Translation - Case Studies Central Dogma: Transcription & Translation - Competitive Exam Level Central Dogma: Transcription & Translation - Higher Difficulty Problems Central Dogma: Transcription & Translation - Numerical Applications Central Dogma: Transcription & Translation - Problem Set Central Dogma: Transcription & Translation - Real World Applications Mendelian Genetics and Heredity Mendelian Genetics and Heredity - Advanced Concepts Mendelian Genetics and Heredity - Applications Mendelian Genetics and Heredity - Case Studies Mendelian Genetics and Heredity - Competitive Exam Level Mendelian Genetics and Heredity - Higher Difficulty Problems Mendelian Genetics and Heredity - Numerical Applications Mendelian Genetics and Heredity - Problem Set Mendelian Genetics and Heredity - Real World Applications Structure of DNA and RNA Structure of DNA and RNA - Advanced Concepts Structure of DNA and RNA - Applications Structure of DNA and RNA - Case Studies Structure of DNA and RNA - Competitive Exam Level Structure of DNA and RNA - Higher Difficulty Problems Structure of DNA and RNA - Numerical Applications Structure of DNA and RNA - Problem Set Structure of DNA and RNA - Real World Applications

Q. During transcription, which enzyme is responsible for synthesizing RNA from a DNA template?

A. DNA polymerase
B. RNA polymerase
C. Ribosome
D. Ligase

Solution

RNA polymerase is the enzyme that synthesizes RNA by transcribing the DNA template during the process of transcription.

Correct Answer: B — RNA polymerase

Q. During transcription, which enzyme synthesizes RNA from a DNA template?

A. DNA polymerase
B. RNA polymerase
C. Ribosome
D. Ligase

Solution

RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during the process of transcription.

Correct Answer: B — RNA polymerase

Q. If a plant with genotype AaBb is crossed with another AaBb plant, what fraction of the offspring will be homozygous recessive for both traits?

A. 1/16
B. 1/4
C. 3/16
D. 9/16

Solution

The fraction of offspring that are homozygous recessive (aabb) from the cross AaBb x AaBb is 1/16.

Correct Answer: A — 1/16

Q. If a trait is controlled by a single gene with two alleles, what is the maximum number of different genotypes possible in a population?

A. 1
B. 2
C. 3
D. 4

Solution

For a single gene with two alleles, the maximum number of different genotypes possible is 3: homozygous dominant, heterozygous, and homozygous recessive.

Correct Answer: D — 4

Q. In a cross between two pea plants, one with round seeds (R) and one with wrinkled seeds (r), what is the phenotype of the F1 generation if round is dominant?

A. Round
B. Wrinkled
C. Both
D. Neither

Solution

The phenotype of the F1 generation will be round seeds since round (R) is dominant over wrinkled (r).

Correct Answer: A — Round

Q. In a dihybrid cross, what is the expected phenotypic ratio in the F2 generation?

A. 3:1
B. 1:2:1
C. 9:3:3:1
D. 1:1:1:1

Solution

The expected phenotypic ratio in the F2 generation of a dihybrid cross is 9:3:3:1, representing the combinations of two traits.

Correct Answer: C — 9:3:3:1

Q. In a dihybrid cross, what is the expected phenotypic ratio of the offspring?

A. 1:1
B. 3:1
C. 9:3:3:1
D. 1:2:1

Solution

The expected phenotypic ratio of a dihybrid cross is 9:3:3:1, representing the combinations of two traits.

Correct Answer: C — 9:3:3:1

Q. In a double helix, the two strands of DNA are held together by which type of bond?

A. Covalent bond
B. Hydrogen bond
C. Ionic bond
D. Disulfide bond

Solution

Hydrogen bonds between complementary nitrogenous bases hold the two strands of the DNA double helix together.

Correct Answer: B — Hydrogen bond

Q. In a pedigree chart, what does a filled circle represent?

A. A male
B. A female
C. An affected individual
D. A carrier

Solution

A filled circle in a pedigree chart represents an affected female individual.

Correct Answer: C — An affected individual

Q. In a test cross, an individual with a dominant phenotype is crossed with which type of individual?

A. Homozygous dominant
B. Heterozygous
C. Homozygous recessive
D. Any individual

Solution

A test cross is performed by crossing an individual with a dominant phenotype with a homozygous recessive individual to determine the genotype.

Correct Answer: C — Homozygous recessive

Q. In a test cross, an individual with an unknown genotype is crossed with a homozygous recessive individual. What is the purpose of this cross?

A. To determine the dominant allele
B. To determine the recessive allele
C. To determine the genotype of the unknown
D. To determine the phenotype of the offspring

Solution

The purpose of a test cross is to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

Correct Answer: C — To determine the genotype of the unknown

Q. In a test cross, what is the purpose of crossing an individual with a homozygous recessive?

A. To determine the dominant allele
B. To identify the genotype of the individual
C. To produce offspring
D. To analyze gene expression

Solution

A test cross with a homozygous recessive individual helps determine the genotype of the individual in question.

Correct Answer: B — To identify the genotype of the individual

Q. In cloning, what is the purpose of using a vector?

A. To provide a means of introducing foreign DNA into a host cell
B. To degrade unwanted DNA
C. To amplify RNA
D. To sequence DNA

Solution

Vectors are used to introduce foreign DNA into host cells, allowing for replication and expression of the inserted gene.

Correct Answer: A — To provide a means of introducing foreign DNA into a host cell

Q. In cloning, what is the role of a vector?

A. To provide a template for DNA synthesis
B. To carry foreign DNA into a host cell
C. To amplify RNA
D. To degrade unwanted DNA

Solution

A vector is a DNA molecule used to deliver foreign genetic material into a host cell for cloning purposes.

Correct Answer: B — To carry foreign DNA into a host cell

Q. In DNA, adenine pairs with which base?

A. Cytosine
B. Thymine
C. Guanine
D. Uracil

Solution

In DNA, adenine pairs with thymine through two hydrogen bonds.

Correct Answer: B — Thymine

Q. In eukaryotic cells, what modification occurs to pre-mRNA before it becomes mature mRNA?

A. Addition of a poly-A tail and 5' cap
B. Splicing out of exons
C. Replication of DNA
D. Translation into protein

Solution

Pre-mRNA undergoes capping at the 5' end and polyadenylation at the 3' end, along with splicing to remove introns, to become mature mRNA.

Correct Answer: A — Addition of a poly-A tail and 5' cap

Q. In eukaryotic cells, where does transcription occur?

A. Cytoplasm
B. Nucleus
C. Mitochondria
D. Ribosome

Solution

Transcription occurs in the nucleus of eukaryotic cells, where the DNA is located.

Correct Answer: B — Nucleus

Q. In Mendelian genetics, what does a homozygous genotype mean?

A. Two different alleles for a trait
B. Two identical alleles for a trait
C. One dominant and one recessive allele
D. A trait that is not expressed

Solution

A homozygous genotype consists of two identical alleles for a specific trait, either dominant or recessive.

Correct Answer: B — Two identical alleles for a trait

Q. In Mendelian genetics, what does the term 'allele' refer to?

A. A variant form of a gene
B. A type of chromosome
C. A phenotype
D. A genetic disorder

Solution

An allele is a variant form of a gene that can result in different traits.

Correct Answer: A — A variant form of a gene

Q. In Mendelian genetics, what does the term 'homozygous' refer to?

A. Having two different alleles for a trait
B. Having two identical alleles for a trait
C. The physical expression of a trait
D. The genetic makeup of an organism

Solution

Homozygous refers to having two identical alleles for a particular trait, either dominant or recessive.

Correct Answer: B — Having two identical alleles for a trait

Q. In recombinant DNA technology, what is the role of a vector?

A. To cut DNA
B. To amplify RNA
C. To transport DNA into a host cell
D. To visualize proteins

Solution

Vectors are DNA molecules used to deliver foreign genetic material into a host cell for replication.

Correct Answer: C — To transport DNA into a host cell

Q. In recombinant DNA technology, what is the role of restriction enzymes?

A. To amplify DNA
B. To cut DNA at specific sequences
C. To ligate DNA fragments
D. To transcribe RNA

Solution

Restriction enzymes cut DNA at specific sequences, allowing for the insertion of DNA fragments into vectors.

Correct Answer: B — To cut DNA at specific sequences

Q. In the context of gene expression, what is the function of a promoter?

A. To enhance mRNA stability
B. To initiate transcription
C. To terminate transcription
D. To splice introns

Solution

A promoter is a DNA sequence that initiates transcription by providing a binding site for RNA polymerase.

Correct Answer: B — To initiate transcription

Q. In the context of gene expression, what is the role of mRNA?

A. To store genetic information
B. To transport amino acids
C. To carry the genetic code from DNA to ribosomes
D. To catalyze biochemical reactions

Solution

mRNA (messenger RNA) carries the genetic code from DNA to ribosomes, where proteins are synthesized.

Correct Answer: C — To carry the genetic code from DNA to ribosomes

Q. In the context of the central dogma, what does 'translation' refer to?

A. The process of copying DNA into RNA
B. The synthesis of proteins from mRNA
C. The replication of DNA
D. The modification of RNA

Solution

Translation is the process by which ribosomes synthesize proteins based on the sequence of mRNA.

Correct Answer: B — The synthesis of proteins from mRNA

Q. In which part of the cell does transcription occur?

A. Nucleus
B. Cytoplasm
C. Ribosome
D. Mitochondria

Solution

Transcription occurs in the nucleus where DNA is transcribed into mRNA.

Correct Answer: A — Nucleus

Q. In which phase of the cell cycle does DNA replication occur?

A. G1 phase
B. S phase
C. G2 phase
D. M phase

Solution

DNA replication occurs during the S phase of the cell cycle.

Correct Answer: B — S phase

Q. What is a codon?

A. A sequence of three nucleotides in DNA
B. A sequence of three nucleotides in RNA
C. A type of amino acid
D. A protein structure

Solution

A codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid or stop signal during protein synthesis.

Correct Answer: B — A sequence of three nucleotides in RNA

Q. What is a common application of gene cloning?

A. Producing insulin
B. Creating vaccines
C. Gene therapy
D. All of the above

Solution

Gene cloning is used in various applications, including producing insulin, creating vaccines, and gene therapy.

Correct Answer: D — All of the above

Q. What is a common method for visualizing DNA after gel electrophoresis?

A. Fluorescent microscopy
B. Ethidium bromide staining
C. Western blotting
D. Southern blotting

Solution

Ethidium bromide staining intercalates with DNA and fluoresces under UV light, allowing visualization of DNA bands.

Correct Answer: B — Ethidium bromide staining

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