Select the incorrect statement.

Options

A. B.thuringiensis forms protein crystals that contain insecticidal proteins during a particular phase of their growth.
B. The proteins encoded by the genes crylAc and cryllAb control the cotton bolloworms, that of crylAb controls corn borer.
C. Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (flies , mosquitoes), coleopterans (beetles) and dipterans (tobacco budworm, armyworm).
D. The activated toxin binds to the surface of midgut epithelial cells and creates pores.

Answer

To solve the question of identifying the incorrect statement from the options provided, we will analyze each statement step by step:

### Step 1: Analyze the First Statement
**Statement:** Bacillus thuringiensis forms protein crystals that contain insecticidal protein during a particular phase of their growth.

**Analysis:**
- Bacillus thuringiensis (Bt) is known for producing protein crystals that contain insecticidal proteins (toxins) during its sporulation phase.
- These proteins are indeed toxic to certain insects.

**Conclusion:** This statement is correct.

### Step 2: Analyze the Second Statement
**Statement:** The protein encoded by the genes CRY-AC and CRY-AB control the cotton bullworms. That of CRY-AB controls corn barrier.

**Analysis:**
- The CRY proteins are indeed produced by Bacillus thuringiensis and are effective against various pests.
- CRY-AC and CRY-AB are known to target specific insects, including cotton bollworms and corn borers.

**Conclusion:** This statement is also correct.

### Step 3: Analyze the Third Statement
**Statement:** Protein produced, which kills the insect, is also correct, but here flies and mosquitos are given, and with that our Lepidoptera is mentioned.

**Analysis:**
- The statement mentions that the proteins target flies and mosquitoes, which belong to the order Diptera, while Lepidoptera includes moths and butterflies.
- The specific insects mentioned, such as Tobacco Budworm and RV Worm, belong to Lepidoptera, while flies and mosquitoes do not.

**Conclusion:** This statement is incorrect because it inaccurately associates the target insects with the wrong order.

### Step 4: Analyze the Fourth Statement
**Statement:** The toxins are inactive in the bacteria and become active in the alkaline pH of the insect gut.

**Analysis:**
- This is a well-established fact about Bacillus thuringiensis toxins. They are produced in an inactive form and become active upon ingestion by the insect due to the alkaline conditions in the gut.

**Conclusion:** This statement is correct.

### Final Answer
The incorrect statement is the **Third Statement**.

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