Select the incorrect statement wrt insertional inactivation

Options

A. Selection of recombinations due to inactivation of antibiotic is a cumbersome procedure .
B. Insertional inactivation of `beta ` -galactosidase of leads to colourless colonies .
C. Insertional inactivation of `beta` -galactosidase of leads to blue colourless colonies .
D. Insertional inactivation , the rDNA is inserted within the coding sequence of an enzyme `beta` -galactosidase

Answer

To solve the question regarding the incorrect statement about insertional inactivation, we can follow these steps:

### Step 1: Understand Insertional Inactivation
Insertional inactivation is a technique used in molecular biology to identify and select genetically modified organisms (transformants) that have taken up foreign DNA. This process typically involves inserting a piece of DNA into a gene that is responsible for producing a detectable product, such as an enzyme.

**Hint:** Think about how inserting DNA into a gene can affect the function of that gene.

### Step 2: Identify the Role of Beta-Galactosidase
Beta-galactosidase is an enzyme that breaks down lactose into glucose and galactose. In the context of insertional inactivation, when a foreign DNA insert is introduced into the gene coding for beta-galactosidase, it disrupts the enzyme's ability to function.

**Hint:** Consider what happens to the enzyme's activity when a foreign DNA sequence is inserted into its coding region.

### Step 3: Analyze the Color Reaction
When a chromogenic substrate is added, transformants (bacteria that have taken up the foreign DNA) will not produce beta-galactosidase and thus will not produce a color change, resulting in colorless colonies. In contrast, non-transformants (bacteria that have not taken up the foreign DNA) will produce the enzyme and will form blue colonies.

**Hint:** Remember the color outcomes for both transformants and non-transformants when the chromogenic substrate is present.

### Step 4: Evaluate the Statements
Now, we can evaluate the statements provided in the question:
1. Selection of recombinants due to inactivation of antibiotic is a cumbersome process. (True)
2. Insertional inactivation of beta-galactosidase leads to colorless colonies. (True)
3. Insertional inactivation of beta-galactosidase leads to blue colored colonies. (False)
4. Insertion and inactivation of rDNA is inserted into the coding sequence of enzyme beta-galactosidase. (True)

**Hint:** Compare each statement with the understanding of insertional inactivation and the color outcomes.

### Step 5: Identify the Incorrect Statement
From the evaluation, the incorrect statement is:
- "Insertional inactivation of beta-galactosidase leads to blue colored colonies." This is false because insertional inactivation leads to colorless colonies.

**Final Answer:** The incorrect statement is option 3.