Chapter 7, Problem 1SA

Summary Introduction

To review:

What CRISPR is and how it is used to edit genes.

Introduction:

CRISPR stands for “clustered regularly interspersed short palindromic repeats”, referring to the way DNA was originally organized in some viruses.

Explanation of Solution

Bacteria regularly incorporate bits of viral DNA into their own circular DNA. This way, when a viral particle infects them and injects its DNA, the bacteria produce RNA strands that are complementary to the viral DNA, which will bind to the viral DNA. The bacteria then use the enzyme Cas9 to cut the DNA bound by the RNA strands into fragments.

Taking inspiration from this immune mechanism of bacteria -

1. The CRISPR technology makes use of a synthetic RNA guide molecule which can bind to the target DNA in a cell.
2. The Cas9 enzyme (guided by the RNA molecule) is used to cut the DNA that has been bound by the RNA.
3. A new gene can be inserted into this position to alter the cell in as needed.
4. A plasmid carrying the DNA for the synthesis of the RNA guide and the Cas9 enzyme can be inserted into target cell for the whole process to occur.

This technology results in more precise editing of the gene.

Conclusion

CRISPR stands for “clustered regularly interspersed short palindromic repeats”, which refers to a type of DNA organization in viruses. This technique takes inspiration from this immune mechanism of bacteria, where the bacterial cell uses an RNA molecule to guide enzymes to cut invading DNA molecules.