Question

MCAT Mini-Tutorial: Eukaryotic Gene Regulation

Answer 1

\({\bf{Overview:}}\)
- does not use operons
- uses RNA splicing, lets the same transcript code for multiple proteins
- changing chromatin structure to increase/decrease frequency of transcription
- regulation of transcription
- post-translational modification

\({\bf{Chromatin~Structure:}}\)
- tightly coiled DNA (heterochromatin) does not get transcribed. must be converted to euchromatin for transcription.
- acetylation: adding acetyl groups to the N-terminus. makes DNA less coiled
- methylation: adding methyl groups. condenses DNA. protection against unwanted gene expression and against viruses/other mobile elements.
- epigenetic inheritance: activation/de-activation of genes that is passed through generations. called epigenetic b/c it doesn't change the DNA transcript.



\({\bf{Transcriptional~Regulation:}}\)
- control elements: noncoding DNA, binds w/ activators/repressors, etc. to control gene expression. must be brought near the promoter to start transcription.
- enhancer: a group of control elements on a diff. region of the chromosome as the promoter
- activator: binds to the control element, brings the enhancer close to promoter
- mediator protein: bind w/ transcription factors, brings enhancer and promoter regions closer
- transcription factor: binds to the promoter, initiates transcription
- insulator: stops enhancers and promoters from binding. uses CTCF protein.
- repressor: bind to the control elements. stops transcription.
- noncoding RNA: short RNA sequences that bind to mRNA.
> silence/interfere with transcription through degradation or cleavage
> may use blocking or histone modification to stop translation of TF's
> protect against retrotransposons

Answer 2

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 2nd Edition Barron's Prep book for the new MCAT