Home
NCERT Soltions
Class 12
Biology
Molecular Basis of Inheritance
In the medium where E. coli was growing, lactose was added, which indu...

In the medium where E. coli was growing, | Class 12 Biology Chapter Molecular Basis of Inheritance, Molecular Basis of Inheritance NCERT Solutions

Welcome to the NCERT Solutions for Class 12 Biology - Chapter Molecular Basis of Inheritance. This page offers a step-by-step solution to the specific question from Exercise 1, Question 10: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 10: 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?

Answer:

Lac operon is a segment of DNA that is made up of three adjacent structural genes, namely, an operator gene, a promoter gene, and a regulator gene. It works in a coordinated manner to metabolize lactose into glucose and galactose.

In lac operon, lactose acts as an inducer. It binds to the repressor and inactivates it. Once the lactose binds to the repressor, RNA polymerase binds to the promoter region. Hence, three structural genes express their product and respective enzymes are produced. These enzymes act on lactose so that lactose is metabolized into glucose and galactose.

After sometime, when the level of inducer decreases as it is completely metabolized by enzymes, it causes synthesis of the repressor from regulator gene. The repressor binds to the operator gene and prevents RNA polymerase from transcribing the operon. Hence, the transcription is stopped. This type of regulation is known as negative regulation.

Negative Regulation

Other Questions of Chapter Molecular Basis of Inheritance

Q: List two essential roles of ribosome during translation.

Why is the Human Genome project called a mega project?

Now, sequencing of total genomes getting is getting less expensive day by the day. Soon it may be affordable for a common man to get his
genome sequenced. What in your opinion could be the advantage and disadvantage of this development?

Define an operon. giving an example, explain an Inducible operon.

Q: What is DNA fingerprinting? Mention its application.

Replication was allowed to take place in the presence of radioactive deoxynucleotides precursors in E.coli that was a mutant for DNA ligase. Newly synthesised radioactive DNA was purified and strands were separated by denaturation. These were centrifuged using density gradient centrifugation. Which of the following would be a correct result?

Q: Group the following as nitrogenous bases and nucleosides:
Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Q: If the sequence of the coding strand in a transcription unit is written as follows:
5-ATGCATGCATGCATGCATGCATGCATGC-3
Write down the sequence of mRNA.

Q: Explain (in one or two lines) the function of the followings:
(a) Promoter
(b) tRNA
(c) Exons

Q: 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

Popular questions of class 12 Biology

Q: What is spermatogenesis? Briefly describe the process of spermatogenesis.

Q: Why is reproduction essential for organisms? Answer

Q: Write a short note on
(a) Adaptations of desert plants and animals
(b) Adaptations of plants to water scarcity
(c) Behavioural adaptations in animals
(d) Importance of light to plants
(e) Effect of temperature or water scarcity and the adaptations of animals.

Q: With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.

Q: What is oogenesis? Give a brief account of oogenesis.

Q: Describe the structure of a seminiferous tubule.

Q: What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

Q: With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.

Q: Explain the Law of Dominance using a monohybrid cross.

Q: What are sacred groves? What is their role in conservation?

Recently Viewed Questions of Class 12 Biology

Taking examples under each category, discuss upstream and downstream processing.

Name the first transgenic cow. Which gene was introduced in this cow?

Q: Diagrammatically represent the experimental steps in cloning and expressing an human gene (say the gene for growth hormone) into a bacterium like E. coli ?

Q: Explain what is meant by biofortification.

What is the main idea behind “Joint Forest Management Concept” introduced by the Government of India?

Q: If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population?

Q: Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)

Which type of food would have lactic acid bacteria. Discuss their useful application.

Give the full form of ELISA. Which disease can be detected using it? Discuss the principle underlying the test.

Q: Explain briefly
(a) PCR
(b) Restriction enzymes and DNA
(c) Chitinase

Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

Read the question carefully and focus on the core concept being asked.
Reference examples and data from the chapter when answering questions about Molecular Basis of Inheritance.
Review previous year question papers to get an idea of how such questions may be framed in exams.
Practice answering questions within the time limit to improve your speed and accuracy.
Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Smart Questions to Ask in a Parent-Teacher Meeting | PTM Made Easy

Parent-Teacher Meetings (PTMs) are more than quick updates on marks — they’re a chance to build a real partnership between home and school. A good Parent-Teacher Meeting conversation helps parents see beyond grades. It opens up insights about a child’s strengths, struggles, emotions and even hidden talents. When parents participate actively, they don’t just track […]

The Secret to Smarter Learning — Building Strong Critical Thinking Skills

In today’s world of endless information , knowing how to think is more important than knowing what to think . From school projects to real – life decisions , critical thinking helps students question ideas , analyze facts and form logical conclusions . But what exactly does critical thinking mean ? Simply put , it’s […]

Study Smarter, Not Harder: Build Productive Habits That Stick

Every student dreams of better grades , stronger focus and more study time – but the real challenge isn’t starting, it’s staying consistent . Building productive study habits is not about studying all day , it’s about studying smart . In today’s fast – paced digital world, distractions are everywhere – from endless phone notifications […]

The Hidden Risks of Online Gaming for Children — Is your child safe while gaming online?

Online gaming has rapidly become one of the most popular pastimes among children. Whether it’s multiplayer mobile games , PC adventures or console challenges , kids are spending more time than ever in the virtual world . On the surface, gaming seems entertaining and even educational – improving hand- eye coordination , teamwork and problem […]

View All Blog Posts

Comments

tussi
Dec 18, 2016

anything incomplete

tussi
Dec 18, 2016

nc answer