gene expression Flashcards
gene expression
all cells in body have same dna but very different morphology
cell differentiation
specialization of cells where they commit to specific morphology
what kinds of cells do stem cells differentiate into
ectoderm, mesoderm, endoderm
hematopoetic stem cells
stem cells of blood cells
totipotent
can differentiate into any type of cell
- applies only to zygote through stage of morula
pleuripotent
differentiate into any germ layer (ecto,endo,meso) obtained from blastocyst
multipotent
describes adult stem cells, can differentiate into several types of a specific cell
olgiopotent
can only differentiate into a few types
apopstosis importance to development
helps establish boundries between organs and structures
operon
gene expression in prokaryotes
- can be under positive or negative control
negative control operon
repressor prevents transcription by binding to an operator
operator
sequence upstream of the first protein coding region
positive control
activator stimulates trascription
lac operon
negative control and inducible
gives ecoli the ability to metabolize lactose
when lactose is present and glucose is active, lactose is metabolized
promoter region
upstream of operator
what happens to lac operon when lactose is NOT present
the represor is bound to the operator and prevents transcription of lactose metabolizing enzymes
when lactose is present what molecule binds to the repressor?
allolactose , which frees the oeprator and transcription may begin
why is the lac operon typically turned off?
because metabolizing lactose when glucose is available is energetically unfavorable
CAP binding sequence
bound by high levels of cAMP
positive control, when bound lactose metabolism is enhanced
what is the function of cap binding proteins
they promote protein synthesis
what is derived from endoderm
internal lining of respiratory tract, digestive tract
liver, pancreas, lungs, epithelial linings
what is derived from ectoderm
epidermis, brain, spinal cord,
what is derived from mesoderm
dermis, heart, bone, bonemarrow, muscle, urogenital system
what is the outcome when no lactose is present and glucose is present?
the repressor is bound to the lac operon and lactose is not metabolized
what happens when lactose is present and glucose is not
cap binds to cap binding sequence, and repressor is bound to allolactose so lactose can be metabolized
trp operon
contains genes that synthesize tryp, is turned off when trp is part of the diet
- trp binds to repressor which binds to the operator and prevents tryptophan synthesis
which operon is an example of repressible negative
trp, turned off in the presence of tryptophan which is the envirnmental change and is naturally on
promoters
upstream regions of dna that initiate transcription
bind to proteins that help recruit RNA polymerase to initiate transcription
example of common eukaryotic promoter
TATA box and CAAT
TATA binding protein
binds to tata box and contributes to the binding of RNA polymerase
transcription factors
proteins that regulate expression by binding to a specific sequence of DNA that recruit proteins that play a role in acetylation and methylation
enhancers
allow increased gene expression , not necessarily close upstream of coding region , bring transcription factors closer to gene
silencers
opposite of enhancers, where repressors bind
histones
positively charged proteins bound to dna
heterochromatin
tight structure of histones and dna