Gene/Protein Expression Flashcards
(31 cards)
what are the examples of molecules that don’t follow the central dogma of molecular biology?
retroviruses
non-coding RNA (rRNA, tRNA)
what is the definition of DNA?
a polymer molecule made up of a string of deoxyribonucleic acids - the sequence contains info to generate new organisms
define the genome
sequence of all DNA in an organism (genes + non-coding regions)
define the gene
unit of inheritance - many code for proteins but not all
what addition sites are added to the gene in the untranslated region?
cap addition site and polyA addition site
what are the 3 steps of transcription?
initiation - RNA polymerate 2 comes to the start of the gene and the DNA strand is pulled apart
elongation - RNA gets longer (forms transcription bubble)
termination - RNA synthesis stops
how is RNA processed into mRNA?
the 5’ cap and 3’ polyA tail is added
introns are removed by splicing using splicosome
mRNA exported to cytoplasm for translation
what are transcription factors?
proteins binding to specific DNA sequences affecting transcription rate
what are the 2 types of transcription factors?
activators and repressors
name 4 examples of transcription factors
p53 and E2F (cell cycle control)
steroids (act on TFs)
nuclear hormone receptors (oestrogen/testosterone)
what is the transcription initiation complex?
transcription factors act as bridge between DNA and RNA polymerase to allow them to bind
where do TFs further stabilise TIC?
upstream enhancer elements
what are enhancers and silencers? where are they found? what do they do?
DNA sequences where TFs bind to affect transcription rate
can be upstream/downstream of a gene, close or far away
make it more likely (enhancer) or less likely (silencer) that a promoter is activated
genes often have several enhancers bound by several TFs
what does p53 activate and repress the transcription of?
activates transcription of p21 (cell cycle arrest/DNA repair)
represses transcription of survivin (apoptosis)
what does ‘closed state’ DNA mean?
TFs have no access to the DNA
how does DNA ‘close’?
wrapped around histones to form nucleosomes, forms a scaffold complex
what are locus control regions? and how do they work?
open chromatin spanning several genes (e.g globin genes)
TFs bind to globin LCR in erythrocytes opening DNA of all globin genes making gene expression possible
what is constitutive gene expression? and give some examples
genes expressed in all cells, all the time, at constant levels
e.g ribosomal proteins and basal TFs
what do all constitutive genes have?
a constitutive promoter
what is inducible gene expression? give examples
genes only expressed in certain tissues/cells at certain times (spatiotemporal gene expression)
e.g CD4/8, collagen type 1, melatonin, inflammatory cytokines
how can one gene produce different products?
splicing (intron removal by splicosome)
what is alternative splicing?
when 1 gene can make more than 1 sequence of mRNA (different isoforms)
name an example of a gene which undergoes alternate splicing
CD45
name an example where alternate splicing can result in disease
the CFTR gene = modifies severity of cystic fibrosis
