Lac Operon

Q.

What is an operator in Lac Operon?

Q.

How many structural genes are present in lac operon?

Q.

In lac operon system, lac i gene codes for :-

1. Inducer

2. Repressor

3. Promoter

4. β-galactosidase

Q.

Is operon present in eukaryotes?

Q.

What are operons in prokaryotes?

Q.

What are operons?

Q.

Y gene in lac operon codes for?

Q. Beta-galactosidase catalyses the hydrolysis of lactose into galactose and glucose.

1. True
2. False

Q.

Which is the prototype operon in bacteria?

Q.

What Is Lac I Gene?

Q.

Match the following genes of the lac operon with their respective products.

Column 1	Column 2
I gene	β-galactosidase
z gene	Permease
A gene	Repressor
Y gene	Transacetylase

Q.

What Are SMC Proteins?

Q. Match the following genes of the Lac operon with their respective products.

a.	i gene	i.	$\beta -$galactosidase
b.	z gene	ii.	Permease
c.	a gene	iii.	Repressor
d.	y gene	iv.	Transacetylase

1. a-iii, b-iv, c-i, d-ii
2. a-i, b-iii, c-ii, d-iv
3. a-iii, b-i, c-ii, d-iv
4. a-iii, b-i, c-iv, d-ii

Q.

What is a major disadvantage to a bacterial cell of having an operon?

Q. Lac operon is the system used by E.coli to

1. Make lactose
2. Breakdown lactose
3. Both A and B
4. Breakdown lactic acid

Q. Match the column:

$\begin{array}{cccc}& \text{Column-I}& & \text{Column-II}\\ \text{(a)}& \text{VNTR}& \text{(i)}& \beta -\text{Galactosidase}\\ \text{(b)}& \text{Lac operon}& \text{(ii)}& \text{DNA ligase}\\ \text{(c)}& \text{Genetic code}& \text{(iii)}& \text{DNA fingerprinting}\\ \text{(d)}& \text{Okazaki fragments}& \text{(iv)}& \text{Unambiguous}\end{array}$

1. a $\to$ iv, b $\to$ ii, c $\to$ iii, d $\to$ i
2. a $\to$ iii, b $\to$ i, c $\to$ iv, d $\to$ ii
3. a $\to$ i, b $\to$ ii, c $\to$ iii, d $\to$ iv
4. a $\to$ iii, b $\to$ iv, c $\to$ i, d $\to$ ii

Q.

Which enzymes will be produced in a cell in which there is a nonsense mutation in the lac Y gene ?

Q. Considering lac operon, match the following:

$\begin{array}{cc}ColumnI& ColumnII\\ p.Regulatorgene& i.Bindingsiteforrepressorprotein\\ q.Operatorgene& ii.Code\left(s\right)fortheproteinoftheenzymes\\ r.Promotergene& iii.Code\left(s\right)forrepressorprotein\\ s.Structuralgenes& iv.BindingSiteforRNApolymerase\end{array}$

1. p-ii, q-i, r-iii, s-iv
2. p-iii, q-i, r-iv, s-ii
3. p-iii, q-iv, r-i, s-ii
4. p-iv, q-i, r-ii, s-iii

Q. Gene regulation governing lactose operon of E. coli that involves the LacI gene product is:

1. Feedback inhibition because excess of $\beta$-galactosidase can switch off transcription
2. Positive and inducible because it can be induced by lactose
3. Negative and inducible because repressor protein prevents transcription
4. Negative and repressible because repressor protein prevents transcription

Q. ‘Lac’ in lac operon refers to

1. Lactic acid
2. Lactose
3. Lactobacillus
4. Levulose

Q.

What does lac in lac operon refer to?

Q. Repressor protein is produced by

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

Q.

Is a promoter a part of an operon?

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

1. Glucose
2. Galactose
3. Lactose
4. Lactose and galactose

Q. Which enzyme/s will be produced in a cell in which there is a nonsense mutation in the lac y gene?

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

Q. In lac operon system, lacI gene codes for

1. Inducer
2. Repressor
3. Promoter
4. $\beta$-galactosidase

Q. The part of an operon producing the repressor is known as

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

Q. Match the column:

$\begin{array}{cccc}& \text{Column-I}& & \text{Column-II}\\ \text{(a)}& \text{VNTR}& \text{(i)}& \beta -\text{Galactosidase}\\ \text{(b)}& \text{Lac operon}& \text{(ii)}& \text{DNA ligase}\\ \text{(c)}& \text{Genetic code}& \text{(iii)}& \text{DNA fingerprinting}\\ \text{(d)}& \text{Okazaki fragments}& \text{(iv)}& \text{Unambiguous}\end{array}$

1. a $\to$ iv, b $\to$ ii, c $\to$ iii, d $\to$ i
2. a $\to$ iii, b $\to$ i, c $\to$ iv, d $\to$ ii
3. a $\to$ i, b $\to$ ii, c $\to$ iii, d $\to$ iv
4. a $\to$ iii, b $\to$ iv, c $\to$ i, d $\to$ ii

Q. In regulation of gene expression in prokaryotes
I. Lactose acts as the suppressor for gene expression.
II. Tryptophan acts as the inducer for gene expression.
III. Regulator gene is the one that produces the repressor molecule.
Which of the statements given above are correct?

1. Only I
2. Only II
3. Only III
4. II and I
5. II and III

Q. At the time of organogenesis, genes regulate the process at different levels and at different times due to:

1. Promoter
2. Regulator
3. Intron
4. Exon