The lactose present in the growth medium of bacteria is transported to the cell by the action of [2024]
beta-galactosidase
acetylase
permease
polymerase
(3)
In the absence of glucose, if lactose is provided in the growth medium of the bacteria, the lactose gets transported into the cells by the action of enzyme permease encoded by lac y gene. A very low level of expression of lac operon has to be present in the cell all the time (otherwise lactose cannot enter the cells).
Match List I with List II. [2024]
| List I | List II | ||
| A. | Frederick Griffith | I. | Genetic code |
| B. | Francois Jacob & Jacque Monod | II. | Semi-conservative mode of DNA replication |
| C. | Har Gobind Khorana | III. | Transformation |
| D. | Meselson & Stahl | IV. | Lac operon |
Choose the correct answer below:
A-III, B-II, C-I, D-IV
A-III, B-IV, C-I, D-II
A-II, B-III, C-IV, D-I
A-IV, B-I, C-II, D-III
(2)
Frederick Griffith - Transformation
Francois Jacob and Jacque Monod - lac operon
Har Gobind Khorana - Genetic code
Meselson and Stahl - Semi-conservative mode of DNA replication
Which one of the following acts as an inducer for lac operon? [2023]
Sucrose
Lactose
Glucose
Galactose
(2)
Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the Lac operon. Therefore, it acts as inducer.
Name the component that binds to the operator region of an operon and prevents RNA polymerase from transcribing the operon. [2023]
Promotor
Regulator protein
Repressor protein
Inducer
(3)
The repressor protein synthesised from regulatory gene (i gene) binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon.
Match List I with List II. [2023]
| LIST I | LIST II | ||
| A. | Gene ‘’ | I. | β-galactosidase |
| B. | Gene ‘’ | II. | Transacetylase |
| C. | Gene ‘’ | III. | Permease |
| D. | Gene ‘’ | IV. | Repressor protein |
Choose the correct answer from the options given below:
A-III, B-IV, C-I, D-II
A-III, B-I, C-IV, D-II
A-II, B-I, C-IV, D-III
A-II, B-III, C-IV, D-I
(4)
Gene ‘’ → Transacetylase
Gene ‘’ → Permease
Gene ‘’ → Repressor protein
Gene ‘’ → -galactosidase
In an E. coli strain i gene gets mutated and its product cannot bind the inducer molecule. If growth medium is provided with lactose, what will be the outcome? [2022]
Only z gene will get transcribed
z, y, a genes will be transcribed
z, y, a genes will not be translated
RNA polymerase will bind the promoter region
(3)
In lac operon, lactose is an inducer. It binds with repressor and inactivates it.
Match the following genes of the Lac operon with their respective products. [2019]
(A) i gene — (i) β-galactosidase
(B) z gene — (ii) Permease
(C) a gene — (iii) Repressor
(D) y gene — (iv) Transacetylase
Select the correct option:
A - (iii), B - (iv), C - (i), D - (ii)
A - (i), B - (iii), C - (ii), D - (iv)
A - (iii), B - (i), C - (ii), D - (iv)
A - (iii), B - (i), C - (iv), D - (ii)
Select the correct match. [2018]
Alec Jeffreys - Streptococcus pneumoniae
Alfred Hershey and Martha Chase - TMV
Matthew Meselson and F. Stahl - Pisum sativum
Francois Jacob and Jacques Monod - Lac operon
(4)
Alec Jeffreys (1984) invented the DNA fingerprinting technique. Alfred Hershey and Martha Chase proved that DNA is genetic material using bacteriophages in an experiment. Matthew Meselson and F. Stahl proved semiconservative mode of replication in bacterium E. coli.
All of the following are part of an operon except [2018]
an operator
structural genes
an enhancer
a promoter
(3)
Operon concept is for prokaryotes that consist of operator gene, promoter gene, regulator gene and structural gene. Structural, operator and regulator genes are also present in eukaryotic gene expression along with enhancer gene but enhancer gene is present only in eukaryotic gene expression. It changes the rate of transcription of structural genes.
Which of the following is required as inducer(s) for the expression of Lac operon? [2016]
Lactose
Lactose and galactose
Glucose
Galactose
(1)
In Lac operon, lactose is an inducer. It binds with suppressor and inactivates it. It allows RNA polymerase access to the promoter and transcription proceeds.
