gene expression Flashcards
where does transcription occur?
nucleus
where does translation occur?
cytoplasm
3 properties of DNA replication
uses DNA pol, uses DNA as template and needs deoxynucelotides
3 properties of RNA transcription
uses RNA pol, uses DNA template and uses ribonucleotides
3 properties of RNA translation
uses ribosome (has enzymatic abilities and enzymes inside it), mRNA as template and uses amino acids.
what is a promoter?
a protein which gives of a signal. A transcription factor will bind to the promoter region and the gene will be transcribed. This can happen in both directions. down stream, with gene and upstream against gene but both times 5’ to 3’. produces product
how can a promoter control a gene when it is not attached to it directly
may bind the transcription factor which will lead to production of a mediator that activates or inhibits the promoter elsewhere on the gene.
turning premRNA to mature mRNA x3
capping
5’ cap prevents degeneration by nucleosomes in the cytoplasm
tailing
poly A at 3’ end to prevent degradation
splicing
interons removed and exons joined by endonucleases
what is an isonine base?
a base which can code for an A, U or C but always produces the same gene. it is a complication of RNA translation.
4 letter code 5’/3’ ( base ) and after translation it is…?
20 letter code with an N and C terminus (amino acids)
stop codons
UAA, UAG, UGA
start codons
AUG
describe the process of translation
initiation
mRNA strand binds to ribosome and AUG Condon is recognised by tRNA anticodon. Once bound the ribosome moves onto next codon.
elongation
N terminus to C terminus is translated and peptide bonds form between the amino acids catalysed by peptidyl transferase
termination
when stop codon is reached ribosome detaches. tRNA and water is released
what determines the phenotype
the genes which determine the proteins which determines the phenotype
why is gene expression important
ability to turn on and off genes because not all genes needed in every cell at all times
what is a gene
stretch of DNA which a chromosomal locus and is the code and regulation for a protein
which prime is DNA transcribed from and what does this make the mRNA primes
transcribed starting from 3’ to 5’ and therefore the complimentary copied strand of mRNA is from 5’ to 3’
describe the process of DNA replication
recognition of origin of replication initiation proteins and DNA pol will bind to this adding a nucleotide on the end so replication can begin
5’ to 3’ chain growth
when replication forks meet replication is terminated
what is a replication fork
the DNA strand is unwound by DNA helicase as far as the gene is needing to be transcribed. after this the DNA is wound together. DNA transcription cannot go any further than this so when the forks meet at this point this is when replication is terminated
describe transcription
promotoer is recognised and RNA pol binds allowing 5’ to 3’ chain growth of the mRNA strand by complimentary base pairing using ribonucleotides and it is then terminated once the stop sequence has been reached
what drives direction of transcription
when a ribonucleotide binds to the template strand pyrophosphate is released driving the reaction in the correct direction
example of a promoter
TATAAA (tatabox) recognised and bound by transcription factor starting a whole sequence of events and transcription factor drives direction of transcription
what happens if DNA is upside down
then transcription factor will still bind the promoter the other way round and direction of transition changes
where does transcription starts from
from the first nucleotide after where the DNA pol is bound. not necessarily start from promoter sequence. this is called +1
