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The expression of z, y, a genes in lac operon is controlled by
The expression of z, y, a genes in lac operon is controlled by
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Solution
The correct option is A regulator
An operon is defined as a cluster of genes under the control of a single promoter. Lac operon is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria. Gene regulation in prokaryotes can be explained with the help of the Lac Operon. It was observed by Jacob and Monod. The lac operon consists of:
- Promoter gene p-The promoter is the binding site for RNA polymerase, the enzyme that performs transcription. The promoter is present at the 5′ end of lacZ and brings about transcription of all the three genes as a single mRNA. This mRNA is translated to give three protein products.
- Regulatory gene i – It codes for the repressor protein.
- z gene – It codes for beta-galactosidase which catalyzes the hydrolysis of lactose into glucose and galactose.
- y gene – It codes for permease which regulates the lactose permeability in the cell.
- a gene – It codes for transacetylase which assists the enzyme beta-galactosidase.
Hence, all these genes help in lactose metabolism. In the absence of the lactose, the regulator gene in lac operon gets transcribed and translated to produce a repressor protein that binds to the operator region. This further stops the transcription of structural genes located downstream to it.
Lactose acts as an inducer in this operon. In the presence of lactose, the repressor is bound to the lactose molecule. This makes the repressor inactive and prevents it from
binding to the operator region. This allows the transcription of the downstream structural genes, that is z, y, a, to occur.
The structural genes are z, y, a, which after transcription and translation produce 𝛃-galactosidase, permease and transacetylase respectively.
An operon is defined as a cluster of genes under the control of a single promoter. Lac operon is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria. Gene regulation in prokaryotes can be explained with the help of the Lac Operon. It was observed by Jacob and Monod. The lac operon consists of:
- Promoter gene p-The promoter is the binding site for RNA polymerase, the enzyme that performs transcription. The promoter is present at the 5′ end of lacZ and brings about transcription of all the three genes as a single mRNA. This mRNA is translated to give three protein products.
- Regulatory gene i – It codes for the repressor protein.
- z gene – It codes for beta-galactosidase which catalyzes the hydrolysis of lactose into glucose and galactose.
- y gene – It codes for permease which regulates the lactose permeability in the cell.
- a gene – It codes for transacetylase which assists the enzyme beta-galactosidase.
Lactose acts as an inducer in this operon. In the presence of lactose, the repressor is bound to the lactose molecule. This makes the repressor inactive and prevents it from
binding to the operator region. This allows the transcription of the downstream structural genes, that is z, y, a, to occur.
The structural genes are z, y, a, which after transcription and translation produce 𝛃-galactosidase, permease and transacetylase respectively.
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