Gene Structure and Chromatin Flashcards
3 components defining a gene (in eukaryotes)
1) transcribed section of DNA molecule and its
2) CIS regulatory elements
3) this section of DNA sequence contributes to a phenotypic trait (influences structure/function of organism)
what does the translated or “protein coding” portion of the gene consist of? how long is it?
average 1200 bp; consists of exons (some exons have UTRs also)
what does the transcribed part of the gene include? average size?
all exons and introns; 27,000 bp
what do exons contain?
protein-coding regions and untranslated sequences (5’ and 3’ UTRs)
what do introns contain?
start with splice donor sites and end with splice acceptor sites
two consequences of alternative splicing
1) can cause some exons to be removed with introns
2) can cause some introns to be used as exons
are CREs (cis-regulatory elements) transcribed?
no
where is the promoter located?
right next to transcriptional start (beginning of exon 1); where the pre-initiation complex forms
how many promoters per gene?
one
characteristics of promoters
binding site for RNA pol, binding site for “general” transcription factors, often have TATA boxes, around 100-1000 bp
where are enhancers located?
often far (100 kbp) from transcriptional start and first exon; can be in introns of same gene, in adjacent gene or downstream
purpose of enhancers
needed for expression in specific tissues/ cell types at specific time
how many enhancers per gene?
several
characteristics of enhancers
bind cell-type specific transcription factors, have transcription factor binding sites (TBSs), around 100-1000 bp long
role of shadow enhancers
redundant, back-up enhancer (functionally equivalent to enhancers)
