Lac Operon

Q.

Name one inducer.

Q.

Is the Lac Operon Anabolic?

Q.

Name the inducer in the lac operon.

Q. Which of the following is true for an operon?

1. They are absent in prokaryotes
2. It consists of a promoter, operator and structural genes
3. A sequence of three nitrogen bases determining a single amino acid
4. Gene responsible for switching on and switching off of other genes

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. Which one of the following acts as an inducer in the regulatory mechanism of operon model?

1. Fructose
2. Glucose
3. Galactose
4. Lactose
5. Sucrose

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.

Lac operon is called negative regulation because__________

1. The repressor protein inhibits the transcription of structural genes.

2. It gets active only in pressure of lactose

3. The structural genes can digest lactose

4. None of these

Q. Select the two correct statements out of the four (a-d) given below about lac operon.

1. Glucose or galactose may bind with the repressor and inactivate it
2. In the absence of lactose the repressor binds with the operator region
3. The z-gene codes for permease
4. This was eluciated by Francois Jacob and Jacque Monod

Q.

Lac operon was proposed by:

1. Watson and Crick

2. Jacob and Monad

3. Johansen

4. Sharp and Roberts

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. In the lac operon of E.coli, which of the following happens when the repressor binds to the operator?

Q. Which of the following statements are true about lac operon?
I. Glucose binds to CAP binding site and activates the operon
II. In the absence of lactose, the repressor binds with the operator region
III. All three structural gene products are not essential for the metabolism of lactose
IV. The operator is a negative regulatory site bound by the lac repressor protein

1. II and III
2. I and II
3. II and IV
4. I and III

Q. Operon is a

Q. Explain how a polycistronic structural gene is regulated by a common promoter and a combination of regulatory genes in a lac-operon.

Q. Match the genes of the Lac operon with the protein it codes for.

1. a-gene
2. Permease
3. y-gene
4. z-gene
5. Transacetylase
6. $\beta$-galactosidase