Chapter 13 Flashcards
Differentiate between the structures of DNA & RNA
DNA is double stranded with deoxyribose and no uracil
- Know the locations and functions of rRNA
rRNA- Found with ribosomes in cytoplasm, helps synthesize proteins
- Transcription: ________________________________________________
synthesis of an RNA molecule from a DNA template
- Draw and label a transcription unit
Promoter, binding site, coding sequence, terminator
- Draw the substrates for transcription
- Describe the bacterial transcription apparatus
Remember that bacteria only have 1 RNA polymerase that transcribes mRNA, tRNA, and rRNA
Differentiate between bacterial RNA polymerase and eukaryotic RNA polymerases
* While bacteria have ___ RNA polymerase that transcribes all RNA (mRNA, tRNA, rRNA),
eukaryotes have _____ RNA polymerases (named with Roman numerals) that transcribe different
RNAs
1, many
- Define and provide the function of the promoter
A region of DNA that proteins bind to to begin transcription
- Know the steps of bacterial transcription using the information below as a guide
Initiation, elongation, termination
Describe what a consensus sequence is and why its presence is important within a promoter
Calculated sequence of most frequent sequences (AAs/nucleotides). Good to determine genetic variants
- General transcription factors (TFs)
o TFs + RNA pol + mediator= basal transcription apparatus
o Required for transcription
- Eukaryotic core promoter:
o immediately upstream of a gene
o basal transcription apparatus binds here—necessary to have any transcription at all
o there are several consensus sequences within the core promoter that are recognized by many
different proteins, but the only one you need to remember is the TATA box
Know the steps of eukaryotic transcription (for RNA polymerase II)
Initiation, elongation, termination
- You should know that RNA pol II
transcribes pre-mRNA
mRNA
Carries DNA in nucleus to ribosomes
tRNA-
In the cytoplasm, transfers amino acids according to genetic sequence
- RNA synthesis is _________ and ____________ to template strand
complementary,antiparallel
- Initiation
o sigma + core RNA polymerase bind to promoter
o unwinds DNA
o nucleotides incorporated—no primer required
▪ 2 phosphates cleaved for each new nucleotide added
o sigma released
- Elongation
o RNA polymerase changes shape & escapes promoter
o RNA polymerase continues adding nucleotides
o unwinding at front of bubble & rewinding behind bubble
o proofreading
o rho-independent terminators
- RNA polymerase transcribes a terminator sequence, which consists of a sequence that
forms a hairpin structure in the RNA followed by several uracils in the RNA - the hairpin structure causes the RNA polymerase to pause
- at this point, only A-U bonds (weak bonds) are holding DNA and RNA together— DNA
and RNA separate
- Transcriptional activator proteins (TAPs)
o stimulate assembly of basal transcription apparatus to increase transcription levels
* remember that TFs and TAPs are specific to eukaryotes
- Initiation
o TFIID contains a ______________ (TBP) which binds to the ____________ within the core promoter
o Holoenzyme (TFs + RNA pol + mediator) binds to _________
▪ TBP of TFIID positions active site of RNA polymerase over start site
o If TAPs bind to regulatory promoter, they interact with the basal transcription apparatus through
the mediator
o TAPs bound to enhancers can also do this by forming a loop in the DNA
* Elongation
o Similar to bacterial elongation
Termination
o Just know that there are proteins that assist to remove the RNA polymerase and the RNA transcript
from the DNA
TATA-binding protein, TATA box, TFIID
- only ________________ of the DNA are transcribed (mostly __________) rather than the ________________
certain regions, gene regions, entire
chromosome
- only ________ DNA strands is transcribed for each gene
1 of the 2
