The discovery, characterization, and the application of the CRISPR/CAS system has revolutionized the study of genetics and genetic engineering. Please select all correct answers regarding its mechanism of action and application. Multiple correct answers are possible, and partial credit will be given.
A. CRISPR sequences in bacteria resemble those from bacteriophage and plamid DNA.
B. For reverse genetics studies, CRISPR/CAS can be used to replace wildtype alleles with mutant alleles which can knockout the function of the target genes.
C. CRISPR is a DNA sequence in the bacterial chromosome.
D. The guide RNA directs CAS to specific DNA sequences.
E. The CRISPR/CAS system was discovered in bacteria, and its natural function is the equivalent of an immune system in bacteria for "remembering" viral infections and for attacking viral DNA in future infections.

A. CRISPR sequences in bacteria resemble those from bacteriophage and plasmid DNA. (The CRISPR sequences are derived from previously invading bacteriophages and pladmids.)

B. For reverse genetic studies, CRISPR /CAS can be used to replace wild type alleles with mutant alleles which can knock out the function of target genes. (CAS 9 introduces double strand break (DSB) in the target sequence which is then repaired by non homologous end joining (NHEJ). NHEJ causes deletion, insertion or frame shift mutation leading to knock out of the target genes.)

C. CRISPR is a bacterial sequence in the bacterial chromosome. ( The sequences are derived from bacteriophages that had infected the bacteria defore.)

D. The guide RNA guides CAS to specific DNA sequences. ( The guide RNA directs CAS nuclease to the target sequences for editing.)

E. The CRISPR/CAS system was discovered in bacteria, and it's natural function is the equivalent of an immune system in bacteria for remembering viral infections and for attacking viral DNA in future infections. (The CRISPR/CAS system provides acquired immunity to bacteria.)

Explanation:

see answer