Explain mRNA (messenger RNA)
encodes the amino acid sequence of a polypeptide
mRNAs are the transcripts of protein coding genes
Explain tRNA (transfer RNA)
brings amino acids to the ribosome during the translation process
Explain rRNA (ribosomal RNA)
Combines with ribosomal proteins to form the ribosome
mRNA is translated into protein at the ribosome
Explain snRNA (Small nuclear RNA)
combines with certain proteins and is involved in RNA processing in eukaryotes
How many RNA polymerase does bacteria have?
One; composed of the core polymerase plus sigma factor
What are the 4 RNA molecules
mRNA, tRNA, rRNA, snRNA
What are the 3 different RNA polymerases in eukaryotes?
RNA polymerase I: 5.8s, 18s, 28s rRNA genes (ribosome)
RNA polymerase II: all protein-coding genes (mRNA) and some snRNA (messenger RNA)
RNA polymerase III: tRNA genes and some snRNAs
Explain the process of bacterial RNA polymerase transcription of DNA
RNA polymerase core enzyme is a multi-subunit complex that synthesizes RNA using DNA as a template
RNA polymerase + sigma factor (holoenzyme) adheres weakly to bacterial DNA and slides along DNA until it reaches a promoter region( -35BP and -10BP regions)
What are the eukaryotic promotor sequences and boxes?
GC box: GGGCGG -70 to -200 base pairs
TATA box: TATAAA -20 to -35 base pairs
CAAT box: CCAAT -80 base pairs
Explain the eukaryotic proteins needed for transcription initiation
TATA box binding protein: a subunit of TFIID; binds to TATA box of gene promoter
TFIID: causes a distortion in the DNA helix allowing for the recruitment of other transcription factors
TFIIB: involved in RNA polymerase interactions - start site recognitio
Explain transcription initiation in eukaryotes
Most common eukaryote promoter sequence is located at position -35 and contains the sequence - 5' - TATAAAA-3' (TATA box)
TBP/TFIID bind to the promoter at the TATA box (-25)
TFIIB binds to promoter
RNA polymerase, TFIIE, and TFIIH are recruited to the pr
For what level of transcription can you use basal transcriptional machine?
basal transcriptional machine; this is sufficient for only a low level of transcription; for increase levels of transcription or tissue specific transcription, the binding of an activator and mediator/adaptor molecule is required
What is the central dogma of molecular bio?
DNA -> RNA -> Protein
Transcription produces which product? (tRNA? mRNA?)
Translation is the synthesis of a polypeptide using information from what?
What is the site of translation?
In prokaryotes, translation of mRNA can begin before transcription has finished, T/F?
A ____________ ______________ is the initial RNA transcript from any gene prior to processing?
Does RNA have one or strands of nucleotides?
The sequence of bases in DNA is the template for what?
Can both strands of DNA code for genes to produce proteins?
Yes; depends which strand the gene is on
Visualize the antisense and sense strand and how they can be complementary to mRNA
The sense strand of DNA has the same sequence as the mRNA; however in mRNA all of the T's are replaced with U's
The antisense strand of DNA is complementary to mRNA and is used as the template for mRNA synthesis
What are the regions of a prokarytic gene?
Promoter: located upstream of the RNA coding sequence and ensure the proper location of transcription initiation
RNA coding sequence: the DNA sequence that is transcribed into RNA
Terminator: a sequence downstream of the RNA coding sequence and specifies
RNA synthesis is catalyzed by what?
RNA polymerase- pries the DNA strands apart and hooks together the RNA nucleotides
What are the 3 stages of transcription?
Explain the initiation stage of transcription
During transcription only one strand of DNA is required for template - the strand serving as the template is called the antisense strand and the other strand is called coding strand or sense strand
What is the number of base pairs where the prokaryotic promoter begins?
-35 bp : 5' - TTGACA- 3'
-10bp: 5' -TATAAT-3' (aka Pribnow box)
Explain the elongation stage
Coding strand and RNA transcript will have the same bases from 5' to 3' - uracil will be substituted for thymine though
Explain the termination stage
Termination occurs at termination site of DNA
RNA polymerase and ner mRNA transcript is released
Compare DNA synthesis to RNA synthesis.
RNA- RNA polymerase, NTPs precursor, no primer needed, uracil pairs with adenine
DNA- DNA polymerase, dNTP precursor, primer required for initiation, thymine pairs with adenine
What are the 4 types of RNA molecules
mRNA, tRNA, rRNA, snRNA
Can RNA polymerase proofread like DNA?
How accurate is transcription compared to replication?
How many nucleotide pairs per helical turn of double helix?
DNA with fixed ends, rotation is prevented
When 10 DNA base pairs is unwound, the DNA will form one supercoil to relieve tension
One supercoil forms for every 10 bp opened up
What causes positive and negative supercoils?
When a protein is tracking through DNA, the ends are unable to rotate
Excess helical turns ahead of RNA polymerase cause positive supercoils
Deficit of helical turns behind the RNA polymerase cause negative supercoils
Termination of transcription can involve intrinsic termination sequences found in the RNA transcript
Regions that form hairpins varying in length from 7-20 bps, include G-C rich regions and is followed by a run of U bases
Termination of transcription can involve extrinsic factors such as the rho protein in prokaryotes
Rho protein attaches to recognition site on the RNA
Rho moves along RNA following RNA polymerase
RNA polymerase pauses at terminator and rho catches up
RHO unwinds DNA-RNA hybrid and pull RNA from the RNA polymerase
Termination: RNA polymerase, rho, and R
Do eukaryotic cells modify RNA after transcription?
Yes; enzymes in the eukaryotic nucleus modify pre-mRNA (RNA processing) before the genetic messages are dispatched to the cytoplasm
During RNA processing, both ends of the primary transcript are usually altered
Also, usually some interior parts of the mol
What is the importance of introns?
Introns are DNA or RNA molecules which do not code for proteins and interrupts the sequence of genes
Some introns contain sequences that may regulate gene expression
Some genes can encode more than one kind of polypeptide, depending on which segments are