Question

Compare the CRISPR-Cas system to the miRNA system discussed in Concept 18.3, including their mechanisms and their functions.

Short answer

The CRISPR-Cas system and miRNA involve RNA molecules bound to a protein complex that attaches to a complementary sequence and leads to its degradation.

However, the CRISPR-Cas system acts as an immune mechanism that protects the bacterial cell against phage infection. On the other hand, miRNA is involved in gene expression.

Step-by-step solution

CRISPR-Cas System

CRISPR (clustered regularly interspaced short palindromic repeats) are DNA repetitive sequences naturally found in bacterial cells.These sequences are derived from phages that infect bacterial cells.

These sequences can be used to destroy similar DNA sequences of phages on subsequent infections.Cas9 (CRISPR-associated protein 9) is an enzyme that acts as a guide to identify and destroy phage DNA.

Thus, the CRISPR-Cas system acts as an antiviral defense system in bacterial cells.

miRNA system

miRNA are small non-coding RNA molecules that occur naturally in eukaryotic cells. These RNA molecules bind to their target mRNA molecule to form a double-stranded RNA to either degrade or inhibit translation.

miRNA system plays a vital role in the post-transcriptional silencing of genes. Thus, they are involved in the regulation of gene expression.

Comparison of CRISPR-Cas System and miRNA system

CRISPR-Cas system is found in prokaryotes, but the miRNA system is located in eukaryotes. CRISPR-Cas system involves RNA molecules that bind to complementary phage DNA sequences.

miRNA system involves RNA molecules that bind to complementary mRNA sequences. However, they both cause the degradation of the target complementary sequences.

Thus, the CRISPR-Cas system acts as an immune system for the bacterial cells against phages, whereas miRNA regulates gene expression.