• January 28, 2022

Biology MCQ on Lac Operon for NEET and Medical Exam 2021

MCQ on Lac Operon: Biology is one of the most important and vital sections in NEET. It includes theories, descriptions, discoveries, diagrams, definitions, explanation of differences and relations. Most of the concepts covered in the NEET syllabus are from the NCERT syllabus of Class 11 & 12. Other related sources make up for the rest of the syllabus.

MCQ on Lac Operon

In this post we are providing you MCQ on Lac Operon, which will be beneficial for you in upcoming NEET, AIIMS, JIPMER, PGIMER, CBSE Board, ICSE Board, Class 12th, 11th.

MCQ on Lac Operon

Q1. Which of these acts as an inducer of the lac operon?
a) Allolactose
b) Lactose
c) Glucose
d) Galactose

View Answer

(a) Allolactose

Q2. Which condition in lac operon facilitates the condition of lac genes being transcribed at high levels ?
a) low glucose, high lactose
b) low glucose, low lactose
c) high glucose, high lactose
d) high glucose, low lactose

View Answer

(a) low glucose, high lactose

Q3. Regulation of the lac operon can be envisioned as regulation of enzyme synthesis by its _______.
a) lactose
b) substrate
c) carbohydrate
d) all of the above

View Answer

(d) all of the above

Q4. Which of the following will be prevented if the activator fastens to the repressor ?
a) Transcription
b) Binding of the RNA polymerase to the promoter
c) Binding of the repressor to the operator
d) Binding of the repressor to the promoter

View Answer

(c) Binding of the repressor to the operator

Q5. Lac operon is an example of _______.
a) only positive regulation
b) only negative regulation
c) both positive and negative regulation
d) sometimes positive sometimes negative

View Answer

(c) both positive and negative regulation

Q6. In Lac-operon, the gene product of LacA gene is _______.
a) Beta-galactoside permease
b) Beta-galactoside transacetylase
c) Beta-galactosidase
d) Beta-galactoside isomerase

View Answer

(b) Beta-galactoside transacetylase

Q7. The sequence of the structural genes in the lac operon is _______.
a) lacA-lacZ-lacY
b) lacZ-lacY-lacA
c) lacZ-lacA-lacY
d) lacA-lacY-lacZ

View Answer

(b) lacZ-lacY-lacA

Q8. The correct option regarding the lac operon in E.coli from the following is _______.
a) Lac operon is switched on in the absence of lactose
b) Lac repressor binds to the lac promoter
c) β-galactosidase is the only enzyme produced in large quantities when lac operon is turned on
d) lac operon messenger RNA is a polycistronic mRNA

View Answer

(d) lac operon messenger RNA is a polycistronic mRNA

Q9. In the presence of lactose, how long does it take for the lac operon to be expressed?
a) when lactose equals glucose concentration
b) when glucose is more than lactose concentration
c) as long as lactose is more than glucose concentration
d) as long as lactose is more than galactose concentration

View Answer

(c) as long as lactose is more than glucose concentration

Q10. Lac Operon will be turned on when _______.
a) Lactose is less than glucose
b) Lactose is less in the medium
c) Lactose in more than glucose
d) Glucose is enough in the medium

View Answer

(c) Lactose in more than glucose

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