Which feature of the DNA double helix allows it to have a uniform diameter?

Complementary base pairing with purines pairing with pyrimidines

Which of the following correctly describes the role of the promoter in the transcription unit?

It provides a binding site for RNA polymerase.

It terminates the process of transcription.

It is the site where translation begins.

It is the sequence that gets transcribed into RNA.

In the Hershey-Chase experiment, which radioactive isotope was used to label the DNA of the bacteriophages?

Radioactive phosphorus ($^{32}P$)

Radioactive nitrogen ($^{15}N$)

In a hypothetical scenario, a mutation occurs in the mRNA sequence changing the start codon AUG to AUA. What is the most likely outcome of this mutation?

The protein synthesis will not initiate.

The protein will be synthesized normally.

The protein synthesis will not initiate.

A different protein will be synthesized starting from AUA.

The protein will be synthesized but with an incorrect amino acid sequence.

Which of the following statements about tRNA is correct?

tRNA has an anticodon loop complementary to the codon on mRNA.

tRNA binds to stop codons to terminate translation.

tRNA is not involved in the process of translation.

tRNA does not have an amino acid acceptor end.

In the Hershey-Chase experiment, which radioactive element was used to label the DNA of bacteriophages?

Radioactive phosphorus ($^{32}P$)

Radioactive nitrogen ($^{15}N$)

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Class 12 Science (PCB)

Biology

Molecular Basis of Inheritance

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Avery-MacLeod-McCarty Experiment

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Codon Table and Amino Acid Prediction

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DNA as Genetic Material: Griffith Experiment

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Learning Objectives

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Understand the molecular basis of inheritance.
Explain the structure and function of DNA and RNA.
Describe the processes of DNA replication, transcription, and translation.
Analyze the role of ribosomes in protein synthesis.
Differentiate between various types of nucleic acids and their functions.
Discuss the significance of the Human Genome Project.
Explain the concept of DNA fingerprinting and its applications.
Understand the implications of mutations in genetic material.

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Revision Notes & Summary

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Molecular Basis of Inheritance

Exercises

Group the following as nitrogenous bases and nucleosides:
- Nitrogenous Bases: Adenine, Thymine, Guanine, Cytosine, Uracil
- Nucleosides: Cytidine, Guanosine
If a double stranded DNA has 20 percent of cytosine, calculate the percent of adenine in the DNA.
If the sequence of one strand of DNA is written as follows:
- 5'-ATGCATGCATGCATGCATGCATGCATGC-3'
- Write down the sequence of complementary strand in 5'-3' direction.
If the sequence of the coding strand in a transcription unit is written as follows:
- 5'-ATGCATGCATGCATGCATGCATGCATGC-3'
- Write down the sequence of mRNA.
Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.
How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
Differentiate between the following:
- (a) Repetitive DNA and Satellite DNA
- (b) mRNA and tRNA
- (c) Template strand and Coding strand
List two essential roles of ribosome during translation.
In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
Explain (in one or two lines) the function of the following:
- (a) Promoter
- (b) tRNA
- (c) Exons
Why is the Human Genome project called a mega project?
What is DNA fingerprinting? Mention its application.
Briefly describe the following:
- (a) Transcription
- (b) Polymorphism
- (c) Translation
- (d) Bioinformatics

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Practice Test – MCQs, True/False

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Multiple Choice Questions

DNA replication is conservative.

DNA replication is semiconservative.

DNA replication is dispersive.

DNA replication is non-conservative.

Correct Answer: B

Solution:

The Meselson-Stahl experiment demonstrated that DNA replication is semiconservative, meaning each daughter DNA molecule consists of one parental and one newly synthesized strand.

Chapter Concept:

Meselson-Stahl Experiment

The DNA polymerase will correct the mismatch automatically.

The mutation will lead to a frameshift mutation.

The DNA structure will become unstable due to improper hydrogen bonding.

The mutation will have no effect on DNA replication.

Correct Answer: C

Solution:

Adenine normally pairs with Thymine via two hydrogen bonds, and Guanine pairs with Cytosine via three hydrogen bonds. If adenine pairs with cytosine, the hydrogen bonding pattern is disrupted, leading to instability in the DNA structure.

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Molecular Basis of Inheritance

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True or False

Correct Answer: True

Solution:

During transcription, only one of the two DNA strands is used as a template to synthesize RNA. This ensures that the RNA sequence is complementary to the DNA template strand.

Chapter Concept :

RNA and Transcription

Correct Answer: True

Solution:

In eukaryotes, DNA is organized into nucleosomes, where the negatively charged DNA is wrapped around positively charged histone octamers. This structure is essential for DNA packaging and regulation.

Chapter Concept :

Packaging of DNA

Correct Answer: True

Solution:

Lactose acts as an inducer by binding to the repressor, changing its shape, and preventing it from binding to the operator. This allows RNA polymerase to access the promoter and transcribe the operon.

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Molecular Basis of Inheritance

Study Action Plan (Sorted by Difficulty)

Avery-MacLeod-McCarty Experiment

High

Codon Table and Amino Acid Prediction

High

DNA as Genetic Material: Griffith Experiment

Learning Objectives

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Revision Notes & Summary

Molecular Basis of Inheritance

Exercises

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Practice Test – MCQs, True/False

Multiple Choice Questions

Q1.What was the primary conclusion of the Meselson-Stahl experiment regarding DNA replication?

Correct Answer: B

Q2.In a hypothetical scenario, a mutation causes adenine to pair with cytosine instead of thymine. What would be the immediate consequence of this mutation during DNA replication?

Correct Answer: C

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True or False

Q1.In transcription, only one strand of DNA is copied into RNA.

Correct Answer: True

Q2.In eukaryotic cells, DNA is packaged into nucleosomes, which consist of DNA wrapped around a histone octamer.

Correct Answer: True

Q3.In the lac operon, the presence of lactose inactivates the repressor, allowing RNA polymerase to transcribe the operon.

Correct Answer: True

High

DNA Fingerprinting

High

Eukaryotic RNA Polymerases

High

Exons, Introns and Split Genes

High

Gene Regulation and Lac Operon

High

Hershey-Chase Experiment

High

HGP Methodologies

High

Lac Operon Structural Genes

High

Leading and Lagging Strand Synthesis

High

Meselson-Stahl Experiment

High

Operon Concept

High

Polynucleotide Chain Structure

High

Purines, Pyrimidines and Base Pairing

High

Replication Fork and DNA Polymerase

High

Salient Features of DNA Double Helix

High

Salient Features of Human Genome

High

Template Strand and Coding Strand

High

Transcription Unit

High

tRNA as Adapter Molecule

High

VNTR and DNA Polymorphism

High

Bacterial Transcription

High

DNA versus RNA as Genetic Material