Unit 3 Chapter 18: Gene Regulation + Expression in Eukaryotes Flashcards
Which two types of DNA elements that control transcription are unique to eukaryotes
- enhancers
- silencers
What distinguishes enhancers and silencers from promoter elements
- can act at large distances
2. can act in either orientation
What do enhancers do
bind activators
- can be more than 100, 000 bps away from promoter
- can be located inside introns or in untranscribed sequence either in the 5’ or 3’ side of the gene
- unique to eukarykotes
What do silencers do
bind repressors
- unique to eukaryotes
- stop transcription
What determines which proteins are synthesized in what tissues
enhancer and silencer-binding transcription factors
What is special about Heat shock genes and eukaryotic genes
each gene having its own promoter/enhancer/silencer combination (like all eukaryotic genes) and euks can mix and match their components for uniq expression
What is heterochromatic
super tightly wound DNA and stains darkly
-not transcribed in contrast to euromatin
What is euromatin
stains lightly
How do females deal with having 2 X chromosomes
condensing it into a state that prevents transcription
- inactivated chromosome = a barr body
How are calico cats calico cats (what trait makes them this way)
Calicos are always females that are heterozygous for an X-linked fur color gene; they have one yellow allele and one black allele. Depending on which X chromosome was inactivated in the cell giving rise to a patch of skin, that patch will be yellow (more orange actually) or black
What is alternative splicing
Sometimes, when splicing the intron out of an RNA, an exon will be spliced out as well, creating a protein that is missing a chunk. The presence or absence of this chunk can affect how the protein functions
Why are tetraploids bigger than diploids
their cells are bigger
What is a genome
all of the hereditary info in an organism including not only genes but also other non gene stretches of DNA
What is chromatin remodelling
occurs before transcription, the stretch of DNA containing the promoter is released from the chromatin so that RNA polymerase can bind to it
Is DNA negatively or positively charged
negatively
What are nucelosomes
DNA wrapped around histones
What is the TATA bindning protein
TBP
-first step in transcription when promoter interacts with it
What are regulatory sequences
sections of DNA (like 5’cap and 3’ tail) that are involved in on controlling activity of genes
What are regulatory transcription factors
proteins that bind to enhancers, silencers or promoter proximal elements
-responsible for expression of genes in certain cell types and at certain stages of development
What are basal transcription factors
interact with promoter and are not restricted to certain cell types
-must be present for transcription to occur but don’t regulate anything
What is the mediator complex
does not bind to DNA, creates physical link between regulatory and basal transcription factors
What is alternative splicing
splicing the same primary RNA transcript in different ways to produce different mature mRNAs and diff proteins
-allows a single gene to code for many products
What is RNA interference
when the lifespan of mRNA is controlled by tiny single stranded RNAs that bind to complementary sequences in the mRNA which prevent it from being translated into a protein
-don’t want a perfect fit
What are the 4 ways that gene expression differs in bacteria and eukaryotes
- packaging (in euks DNA must be relaxed, default state is coiled)
- alternative splicing (bacs have 1-1 ratio of gene to protein)
- complexity
- coordinated expression-operons in bact, rare in euks; regulatory transcription factors allow this in euks)
In multi cellular euks, why are cells different
because they express diff. genes (not because they have diff genes)
What is a tumour suppressor gene
a gene associated with tumour formation when its product does not function normally
