The Question is from neet-botany biomolecules-biology , and it was created by the author K SURESH KUMAR

Question

Which structural modification to a eukaryotic mRNA is MOST crucial for preventing its degradation by exonucleases in the cytoplasm?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
 **Primary Concept**: Eukaryotic mRNA processing and stability
 **Related Topics**: Exonucleases, 5' cap, 3' poly(A) tail, mRNA degradation, splicing
 **Prerequisites**: Understanding of eukaryotic gene expression, mRNA structure, and the role of exonucleases.
## SOLUTION PATHWAY
**Given Information**:
  The question asks about the MOST crucial modification protecting eukaryotic mRNA from cytoplasmic exonuclease degradation.
  Options: Splicing, Adenine methylation, Ribosome association, 5' cap and 3' poly(A) tail.
**Method & Steps**:
 1. Analyze each option's role in mRNA stability.
  Reasoning: Exonucleases degrade mRNA from the 5' and 3' ends.  Modifications protecting these ends are key.
 2. Evaluate the effectiveness of each modification in preventing exonuclease activity.
  Working: 
		*Splicing (A): Removes introns, but doesn't directly protect from exonucleases.
		*Methylation (B):  While methylation plays a role in gene regulation, it's not the primary protection against exonuclease degradation.
		*Ribosome association (C): Ribosomes protect the mRNA segment they are translating, but not the entire molecule.
		*5' cap and 3' poly(A) tail (D): The 5' cap protects the 5' end from exonucleases, while the 3' poly(A) tail protects the 3' end and enhances stability.  This combined protection is the most crucial.
 3. Determine the most crucial modification.
  Result: The 5' cap and 3' poly(A) tail are the most crucial modifications for preventing degradation by exonucleases. 
  Verification: This is consistent with established knowledge of eukaryotic mRNA processing and stability.
 ## OPTION ANALYSIS
A :x: Splicing removes introns, improving the efficiency of translation, but doesn't directly protect against exonuclease degradation.
B :x: Methylation of adenine residues plays a role in gene regulation but is not the primary mechanism protecting against exonuclease degradation.
C :x: Ribosome binding protects the translated region, but not the entire mRNA molecule from exonucleases.
D ✓: The 5' cap and 3' poly(A) tail are crucial for protecting the mRNA from exonuclease degradation. The cap protects the 5' end, while the poly(A) tail protects the 3' end and enhances stability.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the roles of different mRNA modifications:  Students may mistake splicing or methylation as the primary protection against exonucleases.
  How to avoid: Focus on the mechanism of exonuclease action (degradation from the ends) and how each modification addresses this.
  2.Overlooking the combined effect of the 5' cap and 3' poly(A) tail:  Students might focus on only one of these modifications.
  How to avoid:  Remember that both ends need protection for optimal stability.
 **Quick Tips**:
  1.Remember that exonucleases degrade from the ends, so protection at the ends is crucial.
  2.Think of the 5' cap and 3' poly(A) tail as 'protective caps' on the mRNA molecule.

K SURESH KUMAR · Answer

Splicing out of introns

K SURESH KUMAR · Answer

Methylation of specific adenine residues

K SURESH KUMAR · Answer

Association with ribosomes

K SURESH KUMAR · Answer

The correct Option is "Addition of a 5' cap and a 3' poly(A) tail"

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