Regulatory RNA and CRISPR

Quiz Questions

1. Micro-RNAs (miRNAs) inhibit the expression of specific genes mainly by

2. Which statement best describes the main distinction between the origin of the two classes of small regulatory RNAs: siRNA and miRNA?

3. Which statement best describes the distinction between the purposes of the two RNAi pathways within the eukaryotic cell?

4. The enzyme dicer is responsible for

5. All of the following are involved in translating information into proteins EXCEPT:

6. In RNAi, genes are silenced using:

7. Which organism uses CRISPR as a defense system?

Regulatory RNA

Structure of Gene: Prokaryotes ![[Pasted image 20260304105957.png]]

Structure of Gene: Eukaryotes ![[Pasted image 20260304110041.png]]

RNAi

Research: put pigment gene in flower, made it less dark mRNA levels were reduced. Co-suppression What was happening: post translation transcription silencing

Make more of the normal gene, more of the antisense, both interfere

dsRNA more effective at degrading mRNA >100 more effected than sense or antisense can produce interference at a ew molecules per cell

miRNA

Blocks translation of mRNA

1. Trigger dsRNA
2. Dicer cleaves dsRNA into siRNA (short interfering)
3. RNA-induced silencing complex (RISC) binds to the siRNA and separates its strands
4. siRNA binds to complementary mRNA
5. RISC cleaves the mRNA so that it cannot be translated.

miRNA are generated from step-loop precursors

introns -> pre-miRNA (exported to cytoplasm) -> Dicer -> maturation ->

dsRNA comes from viruses

Lin-4

Decrease translation

CRISPR

Clusters of Regularly Interspaces Short Palindromic Repeats

Phages get incorporates into gene Creates pre-crRNA -> crRNA Makes effector complex Blocks phages of same type

CAS9

gRNA (guide RNA) guides Cas9 to target on dsDNA. Cleaves Two bases at PAM bind to target on DNA

removed retroviruses in pigs