You are studying a virus which is immune to natural CRISPR defense systems. The genome of this virus contains a single CRISPR-like repeat unit (containing of one CRISPR-like repeat and one spacer sequence), and you verify that it is expressed upon infection. There are no indications that this apparent repeat unit is translated into a protein, and you confirm that a mutant version of this virus lacking the single CRISPR-like repeat is not longer immune. To examine the mechanism of action of this RNA anti-CRISPR (Racr) system, you carry out the following experiment. You study two different cell types (a version of the susceptible cell lacking a CRISPR system, labeled "CRISPR-", or one containing CRISPR, labeled "CRISPR+") and grow them either alone or in the presence of the virus containing the Racr repeat. You add a chemical crosslinker to the cell (stabilizing interactions between any parts of the cell at the time of crosslinking), isolate Cas9 proteins, and reverse the crosslinking. You examine the RNAS which were associated with Cas9 on a gel, as shown below. The thickness of the band is proportional to abundance in the sample. long short Cell (CRISPR-) Cell (CRISPR+) - Infected Infected cell (CRISPR-) cell (CRISPR+) a) Propose and briefly justify an explanation for why there are two different RNA bands in the "Cell (CRISPR+)" sample. Propose what each of these might represent. b) Based on these data, propose a hypothesis for how the Racr system confers phage immunity, specifying any relevant molecular interactions.
You are studying a virus which is immune to natural CRISPR defense systems. The genome of this virus contains a single CRISPR-like repeat unit (containing of one CRISPR-like repeat and one spacer sequence), and you verify that it is expressed upon infection. There are no indications that this apparent repeat unit is translated into a protein, and you confirm that a mutant version of this virus lacking the single CRISPR-like repeat is not longer immune. To examine the mechanism of action of this RNA anti-CRISPR (Racr) system, you carry out the following experiment. You study two different cell types (a version of the susceptible cell lacking a CRISPR system, labeled "CRISPR-", or one containing CRISPR, labeled "CRISPR+") and grow them either alone or in the presence of the virus containing the Racr repeat. You add a chemical crosslinker to the cell (stabilizing interactions between any parts of the cell at the time of crosslinking), isolate Cas9 proteins, and reverse the crosslinking. You examine the RNAS which were associated with Cas9 on a gel, as shown below. The thickness of the band is proportional to abundance in the sample. long short Cell (CRISPR-) Cell (CRISPR+) - Infected Infected cell (CRISPR-) cell (CRISPR+) a) Propose and briefly justify an explanation for why there are two different RNA bands in the "Cell (CRISPR+)" sample. Propose what each of these might represent. b) Based on these data, propose a hypothesis for how the Racr system confers phage immunity, specifying any relevant molecular interactions.
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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Transcribed Image Text:You are studying a virus which is immune to natural CRISPR defense systems. The genome of this virus contains a single CRISPR-like repeat unit (containing of one CRISPR-like repeat and one spacer sequence), and you verify that it is expressed
upon infection. There are no indications that this apparent repeat unit is translated into a protein, and you confirm that a mutant version of this virus lacking the single CRISPR-like repeat is not longer immune.
To examine the mechanism of action of this RNA anti-CRISPR (Racr) system, you carry out the following experiment. You study two different cell types (a version of the susceptible cell lacking a CRISPR system, labeled "CRISPR-", or one containing
CRISPR, labeled "CRISPR+") and grow them either alone or in the presence of the virus containing the Racr repeat. You add a chemical crosslinker to the cell (stabilizing interactions between any parts of the cell at the time of crosslinking), isolate
Cas9 proteins, and reverse the crosslinking. You examine the RNAs which were associated with Cas9 on a gel, as shown below. The thickness of the band is proportional to abundance in the sample.
Cell
(CRISPR-)
long
T
short
Cell
(CRISPR+)
Infected
Infected
cell (CRISPR-) cell (CRISPR+)
a) Propose and briefly justify an explanation for why there are two different RNA bands in the "Cell (CRISPR+)" sample. Propose what each of these might represent.
b) Based on these data, propose a hypothesis for how the Racr system confers phage immunity, specifying any relevant molecular interactions.
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