Transcription Flashcards
Transcription provides the intermediate between
genetic information DNA and proteins
transcription
the synthesis of RNA from a DNA template
Transcription is catalyzed by
RNA polymerase
RNA is synthesized from
5’ to 3’
Coding strand is also known as
sense strand
template strand is also known as
anti-sense strand
The newly synthesized RNA is ____ to one of the DNA strands called anti-sense strand
complementary
Synthesis of mRNA by RNA polymerase uses a
DNA template strand
Required for transcription
ATP, GTP, CTP and UTP
no RNA primer needed
Sigma subunit of RNA polymerase recognizes the
promoter sequence at the 5’ end of the genes
Transcription initiation and elongation in how is it different from DNA synthesis
no primer is needed
RNA Pol is semi accurate meaning
1 error in 10.000 bp
Why can transcription have a higher error rate
mutations in RNA are not inherited
Mechanisms for transcription termination
intrinsic
Rho-dependent
Operons
a group of genes close together that code for proteins involved in a common metabolic pathway
Transcription of operons is usually regulated by
environmental/metabolic demands
When no lactose is present
repression of Lac operon
- lac I repressor binds to operator sequence and prevents transcription of Lac operon
Transcription in eukaryotes uses how many polymerases
Three RNA polymerases
Unlike prokaryotes, eukaryotic RNA polymerases don’t use
sigma factor
What transitions from transcription initiation to elongation
RNA polymerase II becomes phosphorylated at its C-terminal domain
can no longer bind a mediator complex
The condensation of chromatin in chromosomes does what to gene expression
silences it
The presence of nucleosomes does what to transcription
represses it
Nucleosome sliding does what
exposes different segments of DNA
transcription factors
helix-turn-helix
zinc fingers
leucine zipper
Helix-turn-helix motif
both helices have glutamine or alanine which can H-bond with adenine and guanine
Zinc finger motif
zinc finger proteins are able to wrap around the major groove of DNA
Why is mRNA shorter than template
introns are spliced out
as a result of alternative splicing
a given gene can generate more than one protein product
Alternative splicing explains
why humans are vastly more complex than organisms that have comparable number of genes
Differences between eukaryotes and prokaryotes
5’ cap
splicing
polyadenylation
