Why is the CRISPR-Cas system of bacteria considered an adaptive immunity rather than an innate immunity?

Verified step by step guidance

Understand the difference between innate and adaptive immunity: Innate immunity provides a general, non-specific defense against pathogens, while adaptive immunity involves a specific response that improves upon repeated exposure to the same pathogen.

Recognize that the CRISPR-Cas system allows bacteria to 'remember' previous infections by integrating short sequences of invading viral DNA (called spacers) into their own genome within the CRISPR array.

Note that this memory enables bacteria to specifically recognize and target the same virus if it attacks again, which is a hallmark of adaptive immunity because it involves a learned and specific response.

Contrast this with innate immunity, which does not involve memory or specificity but relies on general defense mechanisms present from birth.

Conclude that because the CRISPR-Cas system adapts based on past infections and provides a targeted defense against specific viruses, it is considered an adaptive immune system rather than an innate one.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

CRISPR-Cas System

The CRISPR-Cas system is a bacterial defense mechanism that captures snippets of DNA from invading viruses and uses them to recognize and cut the same viruses during future attacks. It acts like a genetic memory, allowing bacteria to target specific viral sequences.

Adaptive Immunity

Adaptive immunity refers to a defense system that learns from previous exposures to pathogens, creating a specific and enhanced response upon re-exposure. It involves memory formation, enabling organisms to recognize and respond more effectively to repeated infections.

Innate Immunity

Innate immunity is the first line of defense that provides a general, non-specific response to pathogens. It does not involve memory or specificity and acts immediately upon infection, relying on physical barriers and generalized cellular responses.

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Textbook Question

A bacterial operon is responsible for the production of the biosynthetic enzymes needed to make the hypothetical amino acid tisophane (tis). The operon is regulated by a separate gene, R. The deletion of R causes the loss of enzyme synthesis. In the wild-type condition, when tis is present, no enzymes are made; in the absence of tis, the enzymes are made. Mutations in the operator gene (O⁻) result in repression regardless of the presence of tis. Is the operon under positive or negative control? Propose a model for:

(a) Repression of the genes in the presence of tis in wild-type cells

(b) The mutations.

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