Question

Consider the statements regarding lac operon and choose the correct option
i) Lactose is the substrate for the enzyme β-galactosidase and regulates switching on and off of the operon.
ii) Lac operon consists of three regulatory genes.
iii) Lac operon consists of one structural gene.
iv) Regulation of lac operon by repressor is referred to as positive regulation
A. i only is correct
B. iv only is correct
C. ii and iii only are correct
D. I and ii only are correct
E. iii and iv only are correct

Answer 1

Hint: The lac operon is an operon that is necessary in E. coli and many other enteric bacteria, for transporting and lactose metabolism. Glucose is the favored substrate for most bacteria.

Complete Answer:
- The lac operon is a group with a single promoter operon (transcribed as a special mRNA), or set of genes. The genes in the operon encode proteins that make lactose an energy supply for the bacteria. E. coli's lac operon includes lactose metabolism-related genes. This only is demonstrated by the existence of lactose and lack of glucose.
- The lactose operon or lac operon is an operon that is necessary in E. coli and many other enteric bacteria, for transporting and metabolism of lactose. Glucose is the favored substrate for most bacteria. However, when glucose is absent by the action of beta-galactosidase, the lac operon permits successful lactose digestion.
- There are three genes in the lac operon: lac Z, lac A, and lac Y. They are transcribed under one promoter's regulation as a single mRNA. Lac operon genes include proteins for the lactose use.
- Lac Z encodes a single unit sugar enzyme that separates lactose into monosaccharides and can be added into glycolysis. LacY encodes a conveyor that helps to carry the lactose in the cell. The lac operon also includes many regulatory DNA sequences in addition to the three genes.
- The lac gene protein is recognized as the lac repressor. The regulation type in which the lac operon is regulated is known as negative inducible, which means that until any molecule (lactose) is added, it is shut down by the regulating element.

Thus, the correct answer is A. i.e., i only is correct.

Note: Glucose is the favored substrate for most bacteria. When glucose is absent by the action of beta-galactosidase, the lac operon permits successful lactose digestion. There are three genes in the lac operon: lacZ, lacA, and lacY. The regulation type in which the lac operon is regulated is known as negative inducible.