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3 enzymes transcribed together for lactose metabolism
ß-galactosidase, lactose permease, transacetylase
operon
single unit of genes encoding for enzymes
o (operator)
a gene adjacent to the transcription initiation (involved in transcription control)
i
a gene that encodes a protein that binds to the operator
repressor
normal i gene product
repressor function
blocks transcription when bound to o
the lac operon is an example of this type of regulatory control
negative (binding of the repressor blocks transcription)
cis-acting control elements
affect expression of linked genes on the same DNA molecule
example of a cis-acting control element
the i-gene
negative control
the regulatory protein blocks transcription
positive control
the regulatory protein activates transcription
result of glucose presence in E. coli
lac operon is repressed, even in presence of lactose
enhancer
a regulatory sequence located farther away from the start site (upstream or downstream)
enhancer function
help regulate RNA polymerase by binding transcription factors
cohesin
ring-shaped protein complex that allows contact between the target gene and the transcription factor
function of transcriptional activators
bind to regulatory DNA sequences and stimulate transcription
2 domains of transcriptional activators
DNA binding domain, activation domain
1st mechanism of the activation domain
interact with mediator proteins and general transcription factors
2nd mechanism of the activation domain
modification of chromatin structure
type of chromatin that typically binds transcriptional activators
euchromatin
elongation is regulated by:
direct modulation of RNA polymerase activity, and effects on the chromatin structure
NELF and DSIF
negative regulatory factors that bind to RNA polymerase II and stop elongation
P-TEFb function
resumes transcription by phosphorylation of NELF and DSIF
epigenetics
modification that does NOT happen on the DNA sequence
nucleosome
basic unit of chromatin
nucleosome structure
147 base pairs of DNA wrapped around 2 molecules each of histones H2A, H2B, H3, and H4, with one molecule of H1 bound to the DNA
methods by which chromatin can be altered
histone modification and nucleosome rearrangement
3 types of histone modifications
methylation, acetylation, phosphorylation
purpose of histone acetylation
creates more space between nucleosomes (by neutralizing the + charge on lysine) to allow for transcription
histone acetylation method
an acetyl group is added to lysine on the amino-terminal tail
result of an acetylated histone
chromatin is not condensed, which promotes transcription
result of a deacetylated histone
chromatin is condensed, which represses transcription
purpose of histone methylation
induces chromatin condensing and induces heterochromatin formation, which represses transcription
structural component that promoters/enhancers lack which allows them to bind transcription factors
nucleosomes
chromatin remodeling factors
protein complexes that alter contacts between DNA and histones (elongation factor)
methods used by chromatin remodeling factors
reposition nucleosomes, change nucleosome conformations, and eject nucleosomes from the DNA
epigenetic inheritance
transmission of information that is not in the DNA sequence
structures that facilitate elongation
elongation factors, the phosphorylated C-terminal domain of RNA polymerase II
DNA methylation
methyl groups are added at the 5-carbon position of a cytosine that precedes a guanine
result of DNA methylation
represses transcription in genomic imprinting
genomic imprinting
the expression of some genes depends on whether they come from the mother or the father
long noncoding RNA (lncRNA)
form complexes with proteins that modify chromatin and recruit the complexes to their target sites
miRNA
inhibit translation or degrade mRNA
function of Xist lncRNA
mediates inactivation of the X chromosome in mammals
Xist lncRNA is an example of ____ regulation
negative
Note 
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