Chapter 11.5: Eukaryotic Gene Expression Can Be Regulated after Transcription

Flashcards from Chapter 11.5 of Principles of Life, 3rd Edition.

Alternative splicing

The inclusion or exclusion of particular genomic exons through the selective splicing of specific introns, resulting in differently-functioning or defective proteins

• Seen in Drosophila’s Sxl gene including two or four exons per protein, dependent on being female or male

• Enables more mRNAs to be produced from a smaller number of genes

mRNA stability

How long mRNA remains in the cell before it is degraded

• Can be regulated through the attachment of proteins that inhibit RNA nuclease activity or the activity of functional RNAs that regulate gene expression, like miRNAs

microRNAs (miRNAs)

Functional RNA molecules that reduce gene expression in eukaryotes through the alteration of mRNA stability, binding directly to its structure

Small interfering RNAs (siRNAs)

Functional RNA molecules like miRNAs that are 22 nucleotides long

• Degrades only mRNA molecules that are completely complementary

• Interferes in mRNA translation for mismatched molecules

RNA interference

The silencing of genes through the degradation or inhibition of mRNA molecules by miRNAs or siRNAs, found in many eukaryotes

5’ cap modification

mRNA transcription regulation through the modification of guanine triphosphate (GTP) at the 5’ end of the mRNA molecule, remaining dormant until activated through this process

Translational repressor proteins

Proteins that bind to mRNA and prevent attachment to the ribosome, regulating translation

• Seen with the mRNA that codes for ferritin (an iron-storing protein), with a protein bound when iron levels are low but unbound when iron levels are high

Ubiquitin

A protein that marks other proteins (specifically their lysine residues) for destruction through the formation of a chain that attaches to a proteasome for unfolding and digestion

• Aids in the breaking down of cyclins for gene expression regulation