Theme 3 - Mod 4 - Turning Off the Signal

What does multi-level regulation enable in the cell

Enables the cell to rapidly alter the levels of active proteins in response to internal and external signals

in situ hybridization

Utilized to study expression of one or a few genes of interest

DNA microarray

Examines the expression of thousands of genes at once

Sees what groups of genes are used in a specific manner

Why is DNA microarray useful

Largely useful to visualize variation in gene expression during different stages of development across different cell types and response to different signals

Reverse transcription

Reverse transcriptase enzyme causes fluorescent nucleotides to be utilized and become part of newly synthesized cDNA molecule

What happens when there is equal mixture of each cell type in a DNA microarray

Causes them to compete for synthetic complementary DNA fragments

What causes a slide in DNA microarray to change colour

One gene is more expressed or upregulated making the other one repressed

What does the 5' untranslated region do

Affects translation initiation or serves as targets for protein binding to transport the mRNA to particular locations in the cell

What does the 3' untranslated region do

Sometimes regulates translation by binding with specific proteins

RNA interfering machinery

Causes some mRNA to never be translated

Activated by short, non-coding, regulatory, double-stranded RNA molecules

miRNA

Forms hairpin loops due to complementary base-pairing within the miRNA precursor transcripts

What happens to the hairpin loops

Processed into smaller mRNA fragments that can activate RNA interference machinery

RISC complex

Contains sequences that are complementary to specific target mRNA

Binds to mRNA sequence and inhibits translation

siRNA

Exact complements of their mRNA target

Bind with RISC complex as well as induce cleavage or cutting of the target mRNA causing degradation

What do post-transcriptional modifications allow

For the cell to activate or inactivate specific proteins

Proteasomes

Degrade unneeded or damaged proteins

How are proteins removed from the cell

Get marked for enzymatic degradation

What amino acid is involved in protein degradation

Ubiquitin

How are the proteins marked

Polyubiquitin chain that is attached to the substrate target protein and allows for the proteosome to degrade the tagged protein