Lecture 2 Flashcards
RNA vs. DNA
1) single stranded vs. double stranded
2) uracil vs. thymine
3) ribose (OH) vs. deoxyribose (H) on 2’ carbon
Define mRNA
messenger RNA
-transcripted from template DNA
-translates/codes for proteins
Define tRNA.
-transfer RNA
-pairs codons (mRNA–> anticodon (complimentary) with amino acids (CCA terminus)
Define rRNA
-ribosomal RNA
-combines with proteins to form ribosome for translation
IN Progress What are 3 differences between euk. and prokary. transcription?
1) euk mRNA is more stable
2) coupling of transcription & translation in prok (happen at the same time)
3) polycistronic mRNA (pro) vs single protein coding mRNA (euk)
Which RNA polymerase makes mRNAs in eukaryotes?
RNA polymerase II
What is the role of a promoter in transcription?
binds to RNA polymerase to start transcription and tells RNA polymerase II which direction to go
What characterizes promoter sequences?
flexible and variable to regulate transcription
-tighter bond to polymerase–> increase transcription
-looser bond–> slower
What are the consensus sequences for promoter sequences located in prokaryotes?
-35… -10 sequences upstream of +1 (transcription start)
What are the 4 promoter sequences in eukaryotes?
1) TATA box
2) GC box
3) CAAT box
4) Octamer (OCT) box
What strand is the promoter located on?
on the nontemplate strand (the coding strand)
Define consensus sequence.
where on average specific sequences are found
What are the consensus sequences for promoter sequences located in prokaryotes?
-90…-80…-25… +1
How would a mutation in the consensus sequence affect transcription?
likely alter efficiency of promoter binding–> decrease gene transcription
What is an enhancer?
in euk., increase the level of transcription, can be located upstream OR downstream of gene, can be really far (DNA bends)
What is a silencer?
repress gene transcription by folding DNA to block gene transcription, can also be either up/downstream
What are the 3 mechanisms that euk. use to increase the diversity of their proteins?
1) Alternative Splicing
2) Alternative Promoters
3) Alternative polyadenylation
Define intron.
removed from DNA sequence
Define exon.
coding region (kept in mature mRNA)
Define alternative promoter.
able to initiate transcription at distinct start points (change +1) in diff. cell types
Define alternative polyadenylation.
-addition of a Poly A tail to the 3’ end w/ cleavage –> mature mRNA
Define alternative splicing.
allow for different variants of proteins w/o changing genotype by cutting out/turning off certain gene regions
DNA polymerase vs. RNA polymerase
-replication vs transcription
-primer vs no primer
-both strands vs only template
-uses deoxy (-H) vs uses ribose (-OH)
BOTH: polyemerize 5’–> 3’
