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Eukaryotic Gene Expression - Coggle Diagram
Eukaryotic Gene Expression
Regulation of Chromatin Structure
Histone Modifications
Acetylation: acetyl groups are attached to positively charged lysines in histone tails, which loosens chromatin structure and promotes transcription
Methylation: the addition of methyl groups to certain bases in DNA, usually cytosine, condenses chromatin and leads to reduced/prevented transcription
Epigenetic Inheritance
The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence (ex: behaviors + environment)
Ex: explains why identical twins (genetically identical) that grow up differently can look or act differently; cancer is a result of epigenetic modifications
For the most part, these changes are reveres when gametes are produced, but some can be passed down to offspring
Regulating Transcription Initiation
Proteins can bind to DNA to initiate/boost or inhibit transcription
Control elements: segments of noncoding DNA used as binding sites for transcription factors
General transcription factors: bind to promoter of all genes (TATA box), some bind to proteins, lead to a low rate of transcription ("baseline" level)
Specific transcription factors: bind to control elements of enhancers to activate or repress transcription, this area can bend and attach to the promoter to enhance transcription
Repressors: transcription factors that inhibit transcription by binding to control element areas and prevent bending; can silence genes by removing acetyl groups
Activators: proteins that bind to enhancers and stimulate transcription of a gene; transcription factors can bind directly to activators to prevent them from binding to control elements
Coordinate Control
Eukaryotic genes that are co-expressed can be scattered over different chromosomes; coordinated genes will have the same activators, which will recognize specific control elements and promote simultaneous transcription of genes
Post-Transcriptional Regulation
This regulation can alter gene expression in response to environmental changes
Alternative mRNA splicing: different mRNA molecules produced from the same transcript, depending on which RNA segments are treated as exons and which as introns; controlled by regulatory proteins
Initiation of Translation
Regulatory proteins bind to 5' or 3' end of UTRs (untranslated regions), this either prevents ribosomal attachment or causes mRNA degradation
mRNA can be stored
Protein Processing + Degradation
Regulation can occur during modification or transport of a protein through regulatory proteins
ubiquitin - attach to proteins to mark them for destruction
RNAi
RNA interference, blocks gene expression
microRNA’s (miRNA’s) - small RNA molecules attached to proteins that bind to complementary RNA’s and cause degradation or prevent translation
small interfering RNA’s (siRNA’s) - less common, work similarly to miRNA’s but have a different precursor molecule (both precursors are double-stranded RNA), used in research to disable mRNA’s (and therefore specific genes) in order to study gene function