The Question is from neet-botany , and it was created by the author B VENKAT

Question

A researcher aims to create a transgenic cow that produces human lactoferrin in its milk.  Which promoter would be MOST suitable to drive the expression of the human lactoferrin gene in the mammary gland of the cow?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Gene expression regulation in transgenic animals
 **Related Topics**: Promoters, enhancers, tissue-specific expression, transgenic technology
 **Prerequisites**: Understanding of gene structure, transcription, and translation; knowledge of different types of promoters.
## SOLUTION PATHWAY
**Given Information**:
  The goal is to express a human gene (lactoferrin) specifically in the mammary gland of a cow.
  Four promoter options are given: CMV, β-actin, β-lactoglobulin, and metallothionein.
**Method & Steps**:
 1. Identify the promoter that is specifically active in the mammary gland.
  Reasoning:  A successful transgenic cow will only express the human lactoferrin gene in its mammary gland to produce it in milk.  Therefore, we need a promoter that is active only (or predominantly) in mammary tissue.
 2. Evaluate each promoter option for mammary gland specificity.
  Working: 
            * CMV promoter (Cytomegalovirus promoter):  A strong promoter, but it's not tissue-specific; it drives expression in many cell types. 
            * β-actin promoter:  This promoter is active in most cell types, including muscle cells, and therefore not specific to mammary glands.
            * β-lactoglobulin promoter: This promoter is specifically active in the mammary glands of cows.  β-lactoglobulin is a major protein found in cow's milk, so its promoter is naturally designed to drive expression in this tissue.
            * Metallothionein promoter: This promoter is responsive to heavy metals and is not tissue-specific.
 3. Select the most suitable promoter.
  Result: The β-lactoglobulin promoter is the most suitable option because it exhibits mammary gland-specific expression.
  Verification: The choice aligns with the goal of producing human lactoferrin specifically in cow's milk.
 ## OPTION ANALYSIS
A :x: CMV promoter is not tissue-specific, leading to unwanted expression in other tissues.
B :x: β-actin promoter is also not tissue-specific and would lead to expression in various tissues.
C ✓: β-lactoglobulin promoter is specifically active in mammary glands, ensuring targeted expression of the human lactoferrin gene in the desired location.
D :x: Metallothionein promoter is responsive to heavy metals, and not related to mammary gland specific expression.
 ## LEARNING AIDS
 **Common Mistakes**:
  1. Choosing a non-tissue-specific promoter: This would result in human lactoferrin being produced in unintended tissues, potentially causing harmful side effects.
  2. Not considering the target tissue:  Failing to select a promoter that is active in the mammary gland would render the transgenic approach ineffective.
 **Quick Tips**:
  1. Always consider the tissue specificity of the promoter when designing transgenic organisms.
  2. Research the known expression patterns of promoters before making a selection.

B VENKAT · Answer

CMV promoter

B VENKAT · Answer

β-actin promoter

B VENKAT · Answer

The correct Option is "β-lactoglobulin promoter"

B VENKAT · Answer

Metallothionein promoter

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