Final: miRNA [Part 2]
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31 Terms
What are miRNAs?
Small non-coding RNAs that regulate gene expression.
Approximately how long are mature miRNAs?
About 22 nucleotides.
What is the first step in miRNA creation?
Transcription of the miRNA gene by RNA Polymerase II.
What is the first RNA product called in miRNA biogenesis?
pri-miRNA (primary miRNA).
What structural feature forms in pri-miRNA?
A stem-loop (hairpin) structure.
Why is the hairpin structure important?
It is recognized by processing enzymes.
Which enzyme cuts pri-miRNA into pre-miRNA?
Drosha.
Where does Drosha function?
In the nucleus.
What is pre-miRNA?
A shorter hairpin RNA produced after Drosha cleavage.
Approximately how long is pre-miRNA?
About 70 nucleotides.
Which protein transports pre-miRNA out of the nucleus?
Exportin-5.
Where is pre-miRNA transported after leaving the nucleus?
Into the cytoplasm.
Which enzyme cuts pre-miRNA into mature miRNA?
Dicer.
Where does Dicer function?
In the cytoplasm.
What does Dicer produce?
A short double-stranded miRNA molecule.
What happens to the two strands produced by Dicer?
One becomes the guide strand; the other becomes the passenger and is degraded.
What complex uses mature miRNA to silence genes?
RISC (RNA-Induced Silencing Complex).
What does RISC stand for?
RNA-Induced Silencing Complex.
What region of mRNA do miRNAs usually target?
The 3’ UTR.
What happens if miRNA binds strongly to mRNA?
The mRNA is degraded.
What happens if miRNA binds partially to mRNA?
Translation is repressed.
What is the seed sequence in miRNA?
Bases 2–8 of the mature miRNA.
Why is the seed sequence important?
It determines target specificity.
Which enzyme transcribes miRNA genes?
RNA Polymerase II.
Which enzyme trims pri-miRNA?
Drosha.
Which enzyme generates mature miRNA?
Dicer.
Which transport protein exports pre-miRNA from the nucleus?
Exportin-5.
What is the overall function of miRNA?
To regulate gene expression by reducing protein production.
Are miRNAs coding or non-coding RNAs?
Non-coding RNAs.
What diseases are commonly associated with abnormal miRNA regulation?
Cancer and neurological disorders.
What is the correct order of miRNA biogenesis?
DNA → pri-miRNA → pre-miRNA → mature miRNA → RISC → gene silencing
OR
Polymerase → Drosha → Export → Dicer → RISC