Bio1A03 Theme 3 Module 4 Flashcards

At what stages can gene expression be regulated?

Transcription, RNA processing, mRNA stability, translation, post-translational modification, protein transport, and protein degradation.

Why do cells regulate gene expression at multiple levels?

To precisely control when, where, and how much protein is produced.

What is the primary purpose of in situ hybridization?

To determine where and when a gene is expressed in a tissue or organism.

What molecule does the probe bind to during in situ hybridization?

Complementary mRNA.

What does fluorescence indicate in an in situ hybridization experiment?

The location of the target mRNA and therefore gene expression.

What is meant by spatial gene expression?

Where a gene is expressed within tissues or the organism.

What is meant by temporal gene expression?

When a gene is expressed during development or over time.

Is in situ hybridization best suited for analyzing one gene or thousands of genes simultaneously?

One or a few genes.

What is the purpose of a DNA microarray?

To analyze expression levels of thousands of genes simultaneously.

What is the transcriptome?

The complete set of mRNA molecules expressed by a cell.

Why is reverse transcriptase used in microarray experiments?

To convert mRNA into complementary DNA (cDNA).

Why are fluorescent labels added to cDNA samples?

To measure and compare gene expression levels.

What occurs during hybridization in a microarray experiment?

Labeled cDNA binds to complementary DNA probes on the microarray chip.

What does a red spot on a microarray indicate?

Higher expression in the experimental sample (e.g., cancer cells).

What does a green spot indicate?

Higher expression in the control sample (e.g., normal cells).

What does a yellow spot indicate?

Equal expression in both samples.

What does a black spot indicate?

Little or no expression in either sample.

What does a brighter fluorescent spot indicate?

Greater gene expression.

What does a dimmer fluorescent spot indicate?

Lower gene expression.

How does mRNA stability affect protein production?

More stable mRNA generally produces more protein.

Why must a cell sometimes degrade mRNA to stop gene expression?

Because proteins can continue to be made as long as the mRNA remains available.

What does miRNA stand for?

MicroRNA.

What is the main function of miRNA?

To reduce gene expression after transcription.

What protein complex works with miRNA?

RISC (RNA-induced silencing complex).

Does miRNA bind its target mRNA with perfect or imperfect complementarity?

Imperfect complementarity.

What is the result of miRNA binding to mRNA?

Translation is inhibited.

What structural feature commonly forms during miRNA processing?

A hairpin RNA structure.

What does siRNA stand for?

Small interfering RNA.

Does siRNA bind with perfect or imperfect complementarity?

Perfect complementarity.

What happens after siRNA binds its target mRNA?

The mRNA is cleaved and degraded.

What protein complex functions with siRNA?

RISC.

Which RNA molecule usually inhibits translation without cutting mRNA?

miRNA.

Which RNA molecule typically causes direct mRNA degradation?

siRNA.

Q: What is RNA interference (RNAi)?

A process that reduces gene expression using small RNA molecules.

Which two types of RNA are involved in RNA interference?

miRNA and siRNA.

How do researchers use RNA interference experimentally?

To silence genes and study their functions.

What is post-translational regulation?

Regulation that occurs after a protein has been synthesized.

Name four common post-translational modifications.

Phosphorylation, acetylation, methylation, and cleavage.

Why are post-translational modifications important?

They can activate, deactivate, or alter a protein's function.

What is a proteasome?

A large protein complex that degrades proteins.

What types of proteins are commonly degraded by proteasomes?

Misfolded, damaged, or no-longer-needed proteins (transcription factors, cell cycle regulators, etc).

Why is proteasome activity important?

It helps regulate protein levels and cellular functions.

What is the function of ubiquitin?

It tags proteins for degradation.

What does the attachment of multiple ubiquitin molecules create?

A polyubiquitin chain.

What recognizes polyubiquitin-tagged proteins?

The proteasome.

What happens to a protein after entering the proteasome?

It is unfolded and degraded into small peptides.

True/False: The ubiquitin-proteasome pathway ATP-dependent?

True

What is the correct sequence of events in ubiquitin-mediated protein degradation?

Ubiquitination → Polyubiquitin chain formation → Recognition by proteasome → Unfolding → Degradation

In situ hybridization tells researchers what two things about a gene?

Where it is expressed and when it is expressed.

What technique allows scientists to study thousands of genes simultaneously?

DNA microarrays.

What is the main difference between miRNA and siRNA?

miRNA inhibits translation through imperfect matching, whereas siRNA causes mRNA cleavage through perfect matching.