Gene Regulation 2 Flashcards
(20 cards)
Histones
basic proteins in which DNA wraps around in eukaryotic cells
How do histones acomplish this?
4 of them form a core which DNA is wrapped.
What does the core contain?
Two copies of each histone H2A, H2b, H3 and H4.
Octamer
Core of histones
What does chemical modification to DNA and histones do?
Effects on transcription of genes near those modifications
Histone Acetylation of lysines
change positive charges to neutral ones and help “loosen” chromatin. This favors conversion of heterochromatin to euchromatin.
Where does modification of histones occur?
tails and occurs in abundance.
What are examples of histone modification?
methylation, acetylation, phosphorylation and others
What does DNA cytosine base modication do?
Via methylation, effect the inhibiting transcription of nearby genes.
What happens through generations?
These changes can be passed on through generations, effecting epigenetics.
What is an enhancer?
DNA sequence bound by transcriptional activator proteins. Only found in eukaryotes.
What does an enhancer provide?
allows for tissue specific expression of genes
What is a transcriptional activator?
bind enhancers, and w/ bending of DNA, can be brought into close proximity of the transcriptional machinery at promoter sequence.
Insulator sequences
AKA Silences, are sequences are are like enhancers, but instead operate to inhibit the transcription complex. Bound to proteins that interfere with interactions, thus reducing transcription.
Why is regulation or free iron important?
iron can facilitate formation of reactive oxygen species.
Ferritin
a cellular protein that binds free iron
Transferrin
extracellular protein that transports iron to cells.
Iron Response Element
region on ferritin mRNA (eukaryotes) that can be bound by a protein called IRE-BP.
What does IRE-BP do?
binds iron response element when iron is absent, thus inhibiting translation of ferritin mRNA as the ribosome is blocked.
When iron is abundant…
IRE-BP binds to iron an can’t bind to IRE. This means ferritin is made because the ribosome is not blocked from translation the mRNA.
