Question

In Negative operon:-
Inducer binds with repressor
Co-repressor does not binds with repressor
Co-repressor binds with inducer
CAMP have negative effect on lac operon

Answer 1

In genetics, an operon contains a group of genetic regulatory system under the control of single promoter. It is a functioning unit of DNA which includes encoding enzymes, promoters, operators, and activators.

Complete answer:
An operon is a functional unit of genomic DNA that contains a cluster of genes controlled by a single promoter or a same operator. Each operon along with its DNA sequences acts as binding sites for regulatory proteins that promote or inhibit transcription of genes into mRNA.

More specifically, an operon has a regulatory DNA sequence which has a set of genes including structural genes (generally encoding enzymes), an operator genes and regulatory genes (activators or repressors).

The inducer is a molecule that regulates the expression of genes. An inducer can bind with protein repressors or activators. Operon can be regulated or controlled either negatively or positively by induction or repression.

For instance, the lac operon is a negatively controlled inducible operon which is responsible for the degradation of the milk. The inducer molecule of lac operon is allolactose. The expression of the Lac operon is under the control of lac inducer. If the inducer molecule is present, it binds with the repressor and by changing its conformation, the gene expression is controlled so that it is unable to bind with the operator. Thus, in a Negative inducible operon like lac operon, an inducer is normally bound with a regulatory repressor protein which helps to prevent the transcription of genes on the operon and regulates gene expression.

Hence, the correct answer is option (A).

Note: Operons are absent in eukaryotes but they are highly found in prokaryotic organisms especially in bacteria, viruses and some algae.