Gene Organisation and Transcription Flashcards
Define transcription:
process in which nucleotide information in DNA is copied into RNA
Define a gene
- unit of inheritance
- Housekeeping genes: expressed in all cells, needed for - normal cell function
25% of genes expressed in cell required for cell specific function
Define genome:
- complete DNA sequence of an organism
What are the different types of RNA?
- Functional: tRNA, rRNA, snRNA
- Template for translation: mRNA
What are the types of RNAases?
RNAP I: transcribes rRNA genes
RNAP II: transcribes genes encoding proteins in mRNA
RNAP III: transcribes tRNA and 5S RNA genes (large ribosomal subunit)
What is transcription factor:
- DNA binding proteins, special gene regulators, regulate amount of transcription (activators/repressors)
What to TFs do?
- bind to binding sites and bend DNA
- Interact with one another and BTC to modulate transcription
- Facilitate transcription by helping remodel chromatin and recruiting proteins with enzyme activity that modify histones
What is a gene promoter?
sequence at which transcription complex assembles
What is the initiation step?
elongation reaction of RNA synthesis to build BTC
What is the structure of the gene promotor?
see notes
What occurs during hypo and hyperacylation?
Hyperacylation: gene expression/ open histones
Hypoacylation: gene repression/ closed histones
What is the function of the BTC?
Low level of transcription in absence of other TF, binding site controls rate
What is the structure of TFIID?
TATA binding protein (TBP) + TBP accessory factors (TAFs)
How does the BTC assemble?
see notes
What are the factors affecting gene expression?
- Cell lineage: developmental history of cell traced back to parent cell
- Alterations by signals outside of cell eg. Hormones, growth factors, mechanical stress
- Mutated TF (implicated in gene disorders)
- Abnormal TF expression
At what other levels may gene expression occur?
- Transcription
- RNA processing
- RNA transport
- RNA turnover
- Translational
- Protein activity
What are the splice donor and splice acceptor sites?
Splice donor site: conjunction between exon and intron - end of exon/start of intron
Splice acceptor site: junction between intron and exon - end of intron/start of exon
What does mRNA processing use?
small ribonuclear proteins - snRNP
What does an intron start with?
GU
What does an exon start with?
AG
What is a spliceosome?
all snRNP together
Which snRNP causes cleavage of the donor sequence?
U5 binding to splice acceptor site
What is the structure of pre- mRNA?
- Promotor on 5’ (left arrow of picture)
- Sequence in final mRNA coded discontinuously in DNA
- Exons in the order they are in in DNA
Where does processing occur?
in nucleus
