control of gene expression 1 Flashcards
why if most cells in organisms contain the same DNA are cells so different
due to only a subset of genes being transcribed at any time in a particular cell
TATA box
- a DNA sequence that indicates where a genetic sequence can be read and decoded–> a type of promotor sequence The TATA-binding protein (TBP) is a general transcription factor that binds specifically to a DNA sequence called the TATA box. This DNA sequence is found about 30 base pairs upstream of the transcription start site in some eukaryotic gene promoters.
example of a promotor sequence
TATA BOX
control of transcription initiation
–> polymerase interacts with the proteins when it binds to the promotor region- found int he control region - e.g. TATA box–> allows it to bind and start transcription.
process of initiation in eukaryotes
- TF bind to promotor sequences and forms the basal transcription complex with RNA pol 2
- activator proteins bind upstream the enhance sequences and interact with the basal transcription complex
without transcription factors (which attach to TATA boxes), RNA polymerase 2 cannot..
bind to promotors
cis- acting element
operator -influences expression of genes downstream from it on the same 2 stranded DNA -enhancer upstream from activating sequence -includes promoter very close to the protein coding region and includes the nitration site, where transcription begins and a ‘TATA box’
trans acting regulatory gene
repressor -influences expression of any relevant gene in the same cell, on the same or diff DNA
hows many different RNAs are there that transcribe diff sets of genes in eukaryotes
3
RNA polymerase 1
5.85, 185, 285 rRNA gene
RNA polymerase 2
all protein coding genes, plus snoRNA gene, miRNA genes, siRNA genes and most snRNA genes
RNA polymerase 3
tRNA genes, 5s rRNA genes, some snRNA genes and been for there small RNA
what are rRNA named according to
their s value- refers to rate of sedimentation in an ultracentrifuge–> the larger the s value, the larger the rRNA
what inhibits RNA polymerase 2
alpha-amanitin- from mushrooms -deadly
epigenetic inheritance
was first used to refer to the complex interactions between the genome and the environment that are involved in development and differentiation in higher organisms. Today, this term is used to refer to heritable alterations that are not due to changes in DNA sequence. ep
what interact with basal transcription complex
activator proteins
multiple epigenetic mechanisms can contribute to stable gene repression: state 2
-histone modification -DNA methylation
how does epigenetic mechanisms contribute to stable repression
epigenetic modifications, or “tags,” such as DNA methylation and histone modification, alter DNA accessibility and chromatin structure, thereby regulating patterns of gene expression.
EPIGENENTIC changes are usually..
erased turring formation of germ cells e.g. an individual could be born with gene Y on; however due to chromatin changes it could be switched off. During the multiplication of somatic cells, the chromatin changes are followed through, so gene Y is switched off. However during the producing of germ cells the epigenetic change will not be passed on and gene Y will be on.
formation of the basal transcription complex
- TATA-box binding protein (TBP) binds to the TATA box 2. TBT recruits TFIID complex and the TFIIB to the promotor region 3. RNA polymerase 2 and further transcription factors bind tot he promotor to form the BASAL TRANSCRIPTION COMPLEX
what gene control does methylation and histone modification have
histone modification and direct dna methylation on cytosine helps maintain patterns of gene repression in somatic cells
4 points on bacterial gene expression
- no nuclear mem
- one cytoplasmic compartment
- no histones
- couples transcription and translation
protein synthesis in bacteri
where transcription and translation take place at the same time in the cytoplasm
an operon..
has ONE PROMOTER All genes on that operon are transcribed together mRNA is translated to give separate structures
