Question:medium
In the {lac} operon, the {z} gene codes for :
In the {lac} operon, the {z} gene codes for :
Show Hint
Remember the order Z-Y-A and their enzymes B-P-T: \textbf{Z} $\rightarrow$ \textbf{B}eta-gal, \textbf{Y} $\rightarrow$ \textbf{P}ermease, \textbf{A} $\rightarrow$ \textbf{T}ransacetylase.
Updated On: May 28, 2026
- Permease
- Repressor
- Transacetylase
- Beta-galactosidase
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question
The goal is to identify the specific gene product of the {z} structural gene within the {lac} operon. The {lac} operon is a polycistronic system found in {E. coli} that regulates the metabolism of lactose. It is one of the most studied models of gene regulation in prokaryotes. Step 2: Key Formula or Approach
The {lac} operon consists of a regulatory gene ({i} gene) and three structural genes ({z}, {y}, and {a}). Each gene encodes a specific protein involved in the transport or breakdown of lactose. To solve this, one must memorize the sequence and function of the structural genes: {z} $\rightarrow$ {y} $\rightarrow$ {a}. Step 3: Detailed Explanation
The z gene: This gene encodes the primary metabolic enzyme beta-galactosidase ($\beta$-gal). This enzyme is responsible for hydrolyzing the disaccharide lactose into its two constituent monosaccharides: glucose and galactose. It also converts some lactose to allolactose, which acts as the inducer for the operon.
The y gene: This gene codes for the enzyme permease. Permease is a membrane-bound protein that increases the cell's permeability to $\beta$-galactosides, allowing lactose to enter the bacterial cell more efficiently.
The a gene: This gene codes for transacetylase. While its exact role in lactose metabolism is less critical, it is involved in transferring an acetyl group from acetyl-CoA to certain galactosides.
The i gene: This is the regulatory gene that codes for the repressor protein, which keeps the operon turned off in the absence of lactose.
Step 4: Final Answer
The {z} gene in the {lac} operon is specifically responsible for coding the enzyme beta-galactosidase. Thus, (C) is the correct option.
The goal is to identify the specific gene product of the {z} structural gene within the {lac} operon. The {lac} operon is a polycistronic system found in {E. coli} that regulates the metabolism of lactose. It is one of the most studied models of gene regulation in prokaryotes. Step 2: Key Formula or Approach
The {lac} operon consists of a regulatory gene ({i} gene) and three structural genes ({z}, {y}, and {a}). Each gene encodes a specific protein involved in the transport or breakdown of lactose. To solve this, one must memorize the sequence and function of the structural genes: {z} $\rightarrow$ {y} $\rightarrow$ {a}. Step 3: Detailed Explanation
The z gene: This gene encodes the primary metabolic enzyme beta-galactosidase ($\beta$-gal). This enzyme is responsible for hydrolyzing the disaccharide lactose into its two constituent monosaccharides: glucose and galactose. It also converts some lactose to allolactose, which acts as the inducer for the operon.
The y gene: This gene codes for the enzyme permease. Permease is a membrane-bound protein that increases the cell's permeability to $\beta$-galactosides, allowing lactose to enter the bacterial cell more efficiently.
The a gene: This gene codes for transacetylase. While its exact role in lactose metabolism is less critical, it is involved in transferring an acetyl group from acetyl-CoA to certain galactosides.
The i gene: This is the regulatory gene that codes for the repressor protein, which keeps the operon turned off in the absence of lactose.
Step 4: Final Answer
The {z} gene in the {lac} operon is specifically responsible for coding the enzyme beta-galactosidase. Thus, (C) is the correct option.
Was this answer helpful?
0
Top Questions on Regulation of Gene Expression
- Match the following genes of the lac operon listed in column ‘A’ with their respective products listed in column ‘B’:
\[ \begin{array}{|c|c|} \hline \textbf{A: Gene} & \textbf{B: Products} \\ \hline \text{a. ‘i’ gene} & \text{(i) β-galactosidase} \\ \text{b. ‘z’ gene} & \text{(ii) lac permease} \\ \text{c. ‘a’ gene} & \text{(iii) repressor} \\ \text{d. ‘y’ gene} & \text{(iv) transacetylase} \\ \hline \end{array} \] Select the correct option:
- CBSE Class XII - 2024
- Biology
- Regulation of Gene Expression
- Match List I with List II:
List I List II A Two or more alternative forms of a gene I Back cross B Cross of F1 progeny with homozygous recessive parent II Ploidy C Cross of F progeny with any of the parents III Allele D Number of chromosome sets in plant IV Test cross
Choose the correct answer from the options given below:- NEET (UG) - 2024
- Biology
- Regulation of Gene Expression
- Assertion (A): A patient of ADA-deficiency requires periodic or repeated infusion of genetically-engineered lymphocytes.
Reason (R): Lymphocytes are not immortal, but have life span.- CBSE Class XII - 2025
- Biology
- Regulation of Gene Expression
- Which one of the following is wrongly matched?
- NEET (UG) - 2014
- Biology
- Regulation of Gene Expression
- Want to practice more? Try solving extra ecology questions todayView All Questions
