Chapter 21 Flashcards
Gene expression
going from info in the nucleus on a DNA molecule to getting an actual functioning protein
Nucleotide language to nucleotide language
transcription
nucleotide language to amino acid language
translation
bases in RNA
G=C; A=U
types of RNA
mRNA, rRNA, tRNA
two parts of DNA used for making messenger RNA
coding strand and template strand
coding strand
identical to the RNA except it has T instead of U; it is the non-template strand of the DNA
template strand
serves as a template for RNA synthesis
Basic steps of transcription
- DNA helix is open
- RNA pol binds to DNA
- Reads signal strand 3’ to 5’
- Synthesize mRNA 5’ to 3’
promoter region
where RNA pol binds to DNA; tells RNA pol where it needs to start making RNA
operon model for prok
a group of genes with related functions under control of one promoter
what are the 2 sequences upstream from startpoint for prok promoter
6-nucleotide -10 sequence (TAATAT box or prinbow box);
6-nucleotide -35 sequence
what does a highly conserved region mean
very often it is the same sequence even in different species
RNA proofreading
exonuclease activity of the RNA pol
about how many base pairs does RNA pol bind to
30
termination signal
RNA sequence that when transcribed, stops elongation
2 termination methods
Rho factor or intrinsic termination
intrinsic termination
GC rich region followed by U rich resides near the 3’ end. hairpin loop tends to pull RNA away from DNA
rho factor one
participation of another protein, rho factor. ATP dependent unwinding enzyme that unwinds the new RNA away from the DNA template
polycistronic
one message; many proteins;
single mRNA coding for more than 1 protein
3 characteristics of prok mRNA
polycistronic, no post-transcriptional modifications, immediately available for translation
why is mRNA immediately available in proks
there is no nucleus, so oftentimes a ribosome will latch on and start translating before transcription is even complete
Differences in euk transcription (6)
3 diff polymerases, promoters are more varied, transcription factors, extensive RNA processing, protein-protein interaction, RNA cleavage
transcription factors
required to bind RNA pol
extensive RNA processing really means
post-transcriptional modification
protein-protein interactions
bind to DNA and/RNA
RNA pol I
in nucleolus; synthesizes rRNA
RNA pol II
synthesizes precursor mRNA, snRNA, and microRNAs
RNA pol III
synthesizes small RNAs such as tRNA
RNA pol I promoter
core promoter- extends into sequence that is transcribed;
upstream control element- similar sequence to core promoter
RNA pol II promoter
core promoter composed of initiator (Inr), TATA box, TFIIB recognition element (BRE), downstream promoter element (DPE)
RNA pol III promoter
promoters are entirely downstream of transcription start site
upstream means
it is located before the start site. downstream is after
how are polymerases recruited
based on which promoters there are
how are transcription factors named
TF(roman numeral, letter)
ex. TFIIA
roman numeral for polymerase and letter for its order
starting transcription factor
TFIID, which binds to DNA, then other TFs bind to TFIID
One method of euk termination
euk RNA cleavage
euk RNA cleavage
RNA is cut away from DNA molecule 10-35 nucleotides downstream from a special AAUAAA sequence
4 kinds of euk RNA processing
3’ poly(A) tails, 5’ capping, intron removal, chemical modifications
splicesomes
remove introns
purpose of removing introns
alternative splicing increases variation
