Eukaryotic Gene Regulation Flashcards
what makes each cell different?
All cells have the same gene but:
Genes can be turned off and on
Genes have special activator molecules to turn on the genes
what does the histone tail contain?
lysine and arginine
Genome
nucleotide sequence in DNA
Epigenome
chemical tags added to histones or DNA
do eukaryotes contain operons?
NO
what are the basic stages at which gene Expression can be regulated?
packing/unpacking DNA, transcription, mRNA processing, mRNA transport, translation, protein processing, protein degradation
Epigenetic modifications:
addition/ removal of chemical tags on either Histones and/or DNA;
Chemical tags determine if the DNA will be tightly wrapped around or loose
Acetylation of histone tails
loosens the DNA & activates it - usually increases transcription and gene expression
Methylation of tails
can either tighten or loosen
DNA methylation of cytosine
(usually silences genes)
DNA methylase
add CH3 groups to cytosines to silence the gene
Acetylases
add acetyl groups to histone tails, activating the gene
Deacetylases
silence the gene
Basal transcription rate
regular transcription rate
Enhancer Sequence: r
regions of the DNA lie upstream/ downstream from the promoter that interact with cell specific activators or repressor to enhance the basal rate of transcription or decrease it
What do activators bind to?
the enhancer sequence
role of activators
DNA bending protein Bends molecules→ bringing enhancer region in close proximity to the promoter which enhances RNA polymerase binding & transcription factors binding which increases basal rate of transcription → occurs at transcriptional level
what affects which genes are turned on/off?
Types of Activators
2 types of post transcriptional regulation
alternative RNA splicing
mRNA degradation
Alternative RNA splicing (
variability of exons create a family of proteins
mRNA degradation
lifespan of mRNA- determines amount of protein synthesis→ how quickly it gets degrade= stops gene expression → w/o mRNA gene expression stops
Ubiquitin
death tag
Proteasome
degrades the protein into small enzymes
protein processing & degradation
When a protein is tagged with ubiquitin, the protein is to be degraded and it gets sent to the proteasome which degrades it through enzymes
what do microRNAs and siRNAs do?
bind to the RISC complex and cleaves mRNA
Role of Dicer
cuts dsRNA into small fragments
RNA interference results in
either mRNA degradation or blockage of Translation
