Operon Concept

In lac operon, the lactose acts as

In the lac operon shown above, name the molecule ‘X’ synthesized by ‘i’ gene and name the molecule synthesised by the Z gene:

Proteins $\mathrm{P}1$ and $\mathrm{P}2$  bind to each other to form a complex. This complex has a high binding affinity to a specific element on the promoter sequence of a gene $\mathrm{X}$, thus transcribing it. The product of gene $\mathrm{X}$is responsible for the accumulation of red pigment in some plants. Under drought stress, another protein $\mathrm{P}3$ binds to $\mathrm{P}2$ and prevents its binding to $\mathrm{P}1$ and the plants appear pale. The following table depicts a representation of phenotypes of wild-type and mutant  plants.

Choose the correct statement(s).

In biological systems, proteins (repressors and activators) control gene expression. Repressors bind to promoters and inhibit gene expression. Some promoters require activators for gene expression. These constitute a genetic circuit and are analogous to logic gates in digital electronics. A schematic diagram of a genetic circuit in a cell is shown below. Binding of IPTG to LacI activates transcription from $P_{\mathrm{lac}}$. Binding of arabinose (Ara) to AraC activates transcription from $P_{\mathrm{ara}}$.

 The correct statement(s) regarding the given genetic circuit is/are

For RNA polymerase, which of the following genes provides attachment site?

Select the incorrectly matched pair of the following pairs.

Which of the following genes provides attachment site for RNA polymerase enzyme?

Read the following statements with respect to lac operon, and select the correct option.

A. It has three structural genes.

B. Glucose can act as an inducer.

C. Repressor protein acts in the presence of lactose.

D. Repressor is synthesized by the regulator gene.

The regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is true about regulatory proteins?

You have created a fusion between trp operon and lac operon which encodes the enzymes for tryptophan biosynthesis, under the regulatory control of the lac operator. Under which of the following conditions will tryptophan synthase be induced in the strain that carries the chimeric operator fused operons?

When does the lac operon of E. coli get switched on?

This structural gene synthesizes the $\mathrm{mRNA}$ that translates the permease protein

In an operon, a repressor is synthesised by

In lac operon, the regulator gene is denoted as i–gene. Here the term i denotes for

The regulation of gene expression in eukaryotes occurs at the level of :

A. Transcription level.

B. Processing level.

C. Transport of ribosomal subunits from the nucleus to the cytoplasm.

D. Translation level.

The predominant site for the control of gene expression in prokaryote is

The Lac operon contains three structural genes ${}^{\text{'}}\mathrm{z}^{\text{'}},{\mathrm{y}}^{\text{'}}$ and ${}^{\text{'}}\mathrm{a}^{\text{'}}$ The structural genes code for
i) The $\text{'}\mathrm{z}\text{'}$ gene codes for beta-galactosidase enzyme.
ii) $\text{'}\mathrm{a}\text{'}$ gene does not code for transacetylase enzyme.
iii) The $\text{'}\mathrm{y}\text{'}$ gene codes for enzyme permease.
iv) $\text{'}\mathrm{y}\text{'}$' gene does not code for the enzyme permease.
v) $\text{'}\mathrm{a}\text{'}$ gene codes a transacetylase enzyme.
The correct combination is

A polycistronic structural gene is regulated by a common promoter and regulatory genes. Such arrangement is very common in $\dots \dots .$ and is referred to as $\dots \dots .$

Read the following four statements (A-D):

(A) In transcription, adenine pairs with uracil.

(B) Regulation of lac operon by repressor is referred to as positive regulation.

(C) The human genome has approximately 30,000 genes.

(D) Haemophilia is a sex-linked dominant disease.

How many of the above statements are right?

In E.coli the lac operon gets switched on when :-