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Ch. 15 - Regulation of Gene Expression in Bacteria
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Klug 10th EditionCh. 15 - Regulation of Gene Expression in Bacteria문제 17
15장, 문제 17

How does the molecular mechanism of the CRISPR-Cas system use a viral DNA sequence against that same virus?

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1
Understand that the CRISPR-Cas system is an adaptive immune mechanism in bacteria and archaea that provides resistance against invading viruses (phages) by using sequences derived from the viral DNA itself.
Recognize that when a virus infects a bacterium, the CRISPR system captures a short segment of the viral DNA and integrates it into the bacterial genome at the CRISPR locus as a 'spacer' sequence between repeat sequences.
Learn that these spacer sequences are transcribed into CRISPR RNA (crRNA), which guides the Cas proteins to recognize and bind to the complementary viral DNA sequence during subsequent infections.
Know that the Cas proteins, guided by the crRNA, then cleave the matching viral DNA sequence, effectively neutralizing the virus by cutting its genome and preventing replication.
Summarize that the molecular mechanism uses the viral DNA sequence as a molecular memory to specifically target and destroy the same virus if it attacks again, providing sequence-specific immunity.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

CRISPR-Cas System Overview

The CRISPR-Cas system is an adaptive immune mechanism in bacteria and archaea that protects against viral infections by capturing snippets of viral DNA and integrating them into the host genome as 'spacers'. These spacers serve as a genetic memory to recognize and target the virus in future infections.
추천 영상:
가이드 코스
06:32
Overview of Transcription

Guide RNA and Target Recognition

The CRISPR array is transcribed into RNA, which is processed into guide RNAs that match the viral DNA sequences stored as spacers. These guide RNAs direct the Cas proteins to specifically bind and cleave the complementary viral DNA during subsequent infections, preventing viral replication.
추천 영상:
가이드 코스
06:59
RNA Interference

Cas Protein-Mediated DNA Cleavage

Cas proteins, such as Cas9, act as molecular scissors that cut the viral DNA at the site complementary to the guide RNA. This cleavage disables the virus by breaking its genome, thereby stopping the infection and protecting the host cell from viral damage.
추천 영상:
가이드 코스
05:05
Proteins
관련 실천
교과서 질문

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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