MCB Transcription and RNA Processing

Where are all RNAs synthesized?

in the nucleus

Where is mRNA exported?

to the cytoplasm

What happens when mRNA is exported?

it gets translated in the cytoplasm

What are the building blocks of RNA?

ribonucleotide triphosphates (NTPs)

Does DNA have high, low, or mid fidelity?

high fidelity, faithful (no errors)

Is DNA replication complete or incomplete?

complete; entire genome replicated at each cell cycle

How many times does DNA replicate?

once and only once per cell cycle (avoids re-replication)

What is required for DNA replication?

requires an RNA primer to start

Does RNA have high, low, or mid fidelity?

mid fidelity; somewhat faithful (proofreading present but some errors occur)

Is RNA transcription complete or incomplete?

NOT complete; only a subset of genes transcribed at one time

When does RNA transcription occur?

predominantly in G1 and G2 phases

Does RNA transcription require primer to start?

no

What is RNA’s structure?

ribose sugar, uracil, typically single-stranded, can form double stranded secondary structures

What determines secondary structure?

RNA sequence

What are hairpins or stemloops mediated by?

hydrogen bonds

What are ribosomal RNA (rRNA)?

structural and functional components of the ribosome

What is messenger RNA (mRNA)?

carries genetic code for proteins

What is transfer RNA (tRNA)?

helps incorporate amino acids into polypeptide chains

What RNA’s are necessary for protein synthesis?

rRNA and tRNA

What is a gene?

any DNA sequence that is transcribed into and RNA molecule

RNA is _________ and ______ to the template strand?

complementary, antiparallel

What is a nontemplate strand?

coding strand; when the region encodes for a protein

What end are nucleotides added to the RNA molecule?

3’ end

Where does DNA unwind and rewind?

at the front of the transcription bubble

What is the promoter?

initial binding site of RNA polymerase; specifies which polymerase is used for the different classes of genes to be transcribed

What does transcription require?

DNA template, nucleoside triphosphates (NTPs), and the transcription apparatus

What are nucleoside triphosphates (NTPs)?

the raw materials to build a new RNA molecule

What is the transcription apparatus?

contains the proteins needed to catalyze the synthesis of RNA

What do Pol II promoters consist of?

core and regulatory sequences

What is a core promoter?

bound by basal transcription apparatus

What is the regulatory promoter?

often immediately upstream of core promoter

What are transcription activator proteins?

affect rate of transcription

What are consensus sequences?

compromises the most commonly encountered nucelotides at each site

What indicates pyrimidines in a consensus sequence?

Y

What indicates purines in a consensus sequence?

R

What are the 3 phases of transcription?

initiation, elongation, termination

What happens when TDIID with TBP do during transcription initiation?

binds the TATA box and partially unwinds DNA

What happens during elongation?

TFIIs left behind on the promoter, Pol ll moves along the DNA template

What is Rat1?

during transcription termination, a 5’ - 3’ exonuclease

What is the structure of mRNA?

protein coding region, 5’ UTR, and 3’ UTR

What is the protein coding region?

series of nucleotides specifying the amino acids to be added

What is the 5’ UTR?

necessary for ribosome binding and intron splicing

What is the 3’ UTR?

regulatory role in mRNA stability and translation

Why is the 5’ methyl cap required?

initiates translation

What does the 5’ methyl cap increase and influence?

stability of mRNA and intron splicing

When is the 5’ methyl cap added?

during transcription by an enzyme coupled to Pol II

What is polyadenylation?

approx. 50-250 A’s added to end of transcript, NOT coded in the DNA

Why is the Poly (A) tail important?

increases stability of mRNA and plays role in RNA export from nucleus

What does the Poly (A) tail facilitate?

attachement of the ribosome to the mRNA

What is the goal of intron splicing?

stitch together all the exons of a gene and eliminate intron sequences

Where does intron splicing take place?

in the nucleus

What is a spliceosome?

large and complex molecular machinery that carries out intron splicing

What is necessary for correct splicing?

consensus sequences

What are histone modifications?

acetylation and methylation

What is acetylation?

increases rate of transcription

What is methylation?

decreases rate of transcription