19. Which statement is false? a) In CRISPR-cas system the gRNA guide the cas pro

Question

19. Which statement is false?

a) In CRISPR-cas system the gRNA guide the cas protein to the exact target sequence and then cas cleavage site will cut the target DNA on both strands.

b) T-DNA insertion approach is a knock-out mechanism in Arabidopsis that disrupts the gene of interest and the gene can no longer be transcribed into a functional mRNA. As such, this is an approach which works based on transcriptional regulation of gene expression.

c) In nature, the repeat-spacer segment of the CRISPR-cas defense system in bacteria, can be added to the cell memory every time cell is attacked by a new virus. This addition is through incorporation of viral sequence recognition site to the bacterial chromosome where other repeat-spacers are located.

d) In a knock-out mouse the gene is expressed into mRNA but a mechanism prevents the process that translates mRNA into protein.

Explanation / Answer

a.   In CRISPR-cas system the gRNA guide the cas protein to the exact target sequence and then cas cleavage site will cut the target DNA on both strands is true as according to recent researches, CRISPR/Cas9 can be used to generate knock-out cells or animals by co-expressing a gRNA specific to the gene to be targeted and the endonuclease Cas9. We know endonuclease cut DNA (addgene).

b.   Researches of (Wang, 2008), tried to find out how effective is T-DNA insertional mutagenesis in Arabidopsis so the statement: T-DNA insertion approach is a knock-out mechanism in Arabidopsis that disrupts the gene of interest and the gene can no longer be transcribed into a functional mRNA. As such, this is an approach which works based on transcriptional regulation of gene expression is true.

c.    In a knock-out mouse the gene is expressed into mRNA but a mechanism prevents the process that translates mRNA into protein as si RNAs do the same.

d) In nature, the repeat-spacer segment of the CRISPR-cas defense system in bacteria, can be added to the cell memory every time cell is attacked by a new virus. This addition is through incorporation of viral sequence recognition site to the bacterial chromosome where other repeat-spacers are located. This is the only false statement

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