Molecular Basis of Inheritance

In the lac operon, the z gene codes for :

1. the repressor of lac operon
2. transacetylase
3. permease
4. beta-galactosidase

Which of the following statements about lac-operon is correct?

1. Galactose can act as an inducer of lac operon
2. Gene i is constitutively expressed
3. Lactose activates repressor to bind to the operator
4. Genes i, z, y and a share single common promoter

The lactose present in the growth medium of bacteria is transported to the cell by the action of

1. Beta-galactosidase
2. Acetylase
3. Permease
4. Polymerase

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

1. Statement I is true but Statement II is false
2. Statement I is false but Statement II is true
3. Both Statement I and Statement II are true
4. Both Statement I and Statement II are false

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?

1. Only z gene will get transcribed
2. z, y, a genes will be transcribed
3. z, y, a genes will not be translated
4. RNA polymerase will bind the promoter region

In lac operon, z gene codes for

1. Transacetylase
2. β-galactosidase
3. Permease
4. Repressor

Select the correct match :

1. Alec Jeffreys - Streptococcus pneumoniae
2. Alfred Hershey and Martha Chase - TMV
3. Matthew Meselson and F. Stahl - Pisum sativum
4. Francois Jacob and Jacques Monod - Lac operon

All of the following are part of an operon except

1. an operator
2. structural genes
3. an enhancer
4. a promoter

Which of the following is required as inducer(s) for the expression of Lac operon?

1. lactose
2. lactose and galactose
3. glucose
4. galactose

Gene regulation governing lactose operon of E. coli that involves the lac I gene product is

1. negative and inducible because repressor protein prevents transcription.
2. positive and inducible because it can be induced by lactose
3. negative and repressible because repressor protein prevents transcription
4. feedback inhibition because excess of -galactosidase can switch off transcription

Which enzyme will be produced in a cell in which there is a non-sense mutation in the lac Y gene ?

1. Transacetylase
2. Lactose permease and transacetylase
3. Lactose permease
4. -galactosidase

In an inducible operon, the genes are :

1. usually expressed unless a signal turns them "off"
2. always expressed
3. never expressed
4. usually not expressed unless a signal turns them "on"

Read the following four statements (A-D) : How many of the above statements are right ?

1. Four
2. Two
3. Three
4. One

The lac operon consists of -

1. Three regulatory genes and three structural genes
2. Four regulatory genes only
3. Two regulatory genes and two structural genes
4. One regulatory gene and three structural genes

Select the two correct statements out of the four (A–D) statements given below about lac operon. The correct statements are :

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

E. coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because -

1. They cannot transport lactose from the medium into the cell
2. They cannot synthesize functional -galactosidase
3. In the presence of glucose, E. coli cells do not utilize lactose
4. The lac operon is constitutively active in these cells

What does "lac" refer to in what we call the lac operon?

1. The number 1,00,000
2. Lac insect
3. Lactase
4. Lactose

Jacob and Monod studied lactose metabolism in E. coli and proposed operon concept. Operon concept is applicable for :

1. All prokaryotes and all eukaryotes
2. All prokaryotes and some protozoans
3. All prokaryotes
4. All prokaryotes and some eukaryotes

In E. coli, during lactose metabolism repressor binds to : -

1. Promoter gene
2. Operator gene
3. Structural gene
4. Regulator gene

In Negative operon : -

1. cAMP has negative effect on lac operon
2. Co-repressor binds with inducer
3. Co-repressor binds with repressor
4. Co-repressor does not bind with repressor