BI255- TRANSCRIPTION AND TRANSLATION EXAM QUESTIONS
AND ANSWERS LATEST UPDATE
The Central Dogma
states that DNA makes RNA, which then makes proteins
- DNA encodes the information that makes proteins, and it is those proteins that do the
work of the cell
- RNA carries the information from DNA to the protein-making machinery of the cell
RNA is similar but not identical to DNA
- RNA is single-stranded
- RNA uses a ribose sugar (2 -OH bonded to base)
- RNA uses uracil (base pairs with adenine)
RNA forms secondary structures
because RNA is single-stranded, it is energetically favorable for some regions of the
molecule to base-pair with other regions, as long as there is sequence complementarity
- RNA forms hairpins on purpose, shape determines function
- can base pair outside of the molecule because RNA is single stranded and
phosphodiester bonds are flexible
- bases flip out and hydrogen bond with each other to stabilize the secondary structure
DNA transcription makes RNA
because of the similarity of RNA and DNA structure, the synthesis of RNA is templated
off the sequence of DNA
- U's stand in for T's
mRNA
messenger RNAs, code for proteins, store information
rRNAs
ribosomal RNAs, form the basic structure of the ribosome and catalyze protein
synthesis
tRNAs
transfer RNAs, central to protein synthesis as adaptors between mRNA and amino
acids
- store information and are catalytic
snRNAs
small nuclear RNAs, function in a variety of nuclear processes, including the splicing of
pre-mRNA
snoRNAs
small nucleolar RNAs, help to process and chemically modify rRNAs
miRNAs
micronRNAs, regulate gene expression by blocking translocation of specific mRNAs
and cause their degradation
siRNAs
small interfering RNAs, turn off gene expression by directing the degradation of
selective mRNAs and the establishment of compact chromatin structures
, RNA polymerase synthesizes RNA
RNA polymerase, just like DNA polymerase, can only synthesize 5' to 3' & read 3' to 5'
- has its own helicase domain, makes P.D. bond, doesn't require primer, cleaves
phosphate to use its energy
RNA vs DNA polymerases
DNA polymerase: synthesized 5' to 3', read 3' to 5', requires RNA or DNA primer, has a
3' to 5' exonuclease proofreading activity
RNA polymerase: synthesized 5' to 3', read 3' to 5', does not require a primer, does not
have any proofreading activity because RNA is not a permanent molecule, so quality
control is less stringent
RNA Polymerase I
transcribe and visit RNA only genes- not made into proteins (functional RNA); enzyme
that transcribes ribosomal RNA (rRNA) and is essential for protein translation
RNA Polymerase II
main one we talk about, "central dogma"- makes mRNA; all protein-coding genes
RNA Polymerase III
visit RNA only genes- functional pol. that is not made into proteins; tRNA genes, 5S
rRNA genes, some snRNA genes, and genes for other small RNAs
Promoters indicate transcription start points
promoters are double stranded and they are the four distinct DNA sequences arranged
near each other close to the start of the gene
- most transcriptional start sites only have 2 or 3 of the consensus sequences above
- promoter order from left to right: BRE (-35: 35 nucleotides away from start site), TATA
(-30), INR, DPE (+30)
- INR and DPE can become RNA
- these promoters are important because RNA polymerase can't land on a gene by itself
- +1 in front of the INR means that it is the first RNA nucleotide of the transcript that is
made into RNA
- -1 behind the INR means that it is not made into RNA
Transcription start site
precise DNA nucleotide that is turned into the first RNA nucleotide by RNA polymerase
Transcription factors
position RNA polymerase at the correct DNA sequence where transcription is supposed
to begin, and help to initiate transcription
- TFIID and TFIIH have many subunits (separate polypeptides that make it up) because
they do a ton of work
Transcription initiation
Process:
- TFIID (most important TF for identifying a gene) binds TATA box (or another
consensus sequence, if TATA is not there) and when it binds to the promoter, it will
bend it to attract other transcription factors
- bending the promoter attracts TFIIB which checks TFIID's work by making sure that
the right gene is turned on because if it is the wrong gene that can be a critical mistake
- TFIIB binds TFIID if it is in the right spot and it looks for BRE
- Once TFIIB & TFIID are in agreement, they bring in RNA polymerase (inactive form-
positioned at the promoter but not on yet) and other transcription factors
AND ANSWERS LATEST UPDATE
The Central Dogma
states that DNA makes RNA, which then makes proteins
- DNA encodes the information that makes proteins, and it is those proteins that do the
work of the cell
- RNA carries the information from DNA to the protein-making machinery of the cell
RNA is similar but not identical to DNA
- RNA is single-stranded
- RNA uses a ribose sugar (2 -OH bonded to base)
- RNA uses uracil (base pairs with adenine)
RNA forms secondary structures
because RNA is single-stranded, it is energetically favorable for some regions of the
molecule to base-pair with other regions, as long as there is sequence complementarity
- RNA forms hairpins on purpose, shape determines function
- can base pair outside of the molecule because RNA is single stranded and
phosphodiester bonds are flexible
- bases flip out and hydrogen bond with each other to stabilize the secondary structure
DNA transcription makes RNA
because of the similarity of RNA and DNA structure, the synthesis of RNA is templated
off the sequence of DNA
- U's stand in for T's
mRNA
messenger RNAs, code for proteins, store information
rRNAs
ribosomal RNAs, form the basic structure of the ribosome and catalyze protein
synthesis
tRNAs
transfer RNAs, central to protein synthesis as adaptors between mRNA and amino
acids
- store information and are catalytic
snRNAs
small nuclear RNAs, function in a variety of nuclear processes, including the splicing of
pre-mRNA
snoRNAs
small nucleolar RNAs, help to process and chemically modify rRNAs
miRNAs
micronRNAs, regulate gene expression by blocking translocation of specific mRNAs
and cause their degradation
siRNAs
small interfering RNAs, turn off gene expression by directing the degradation of
selective mRNAs and the establishment of compact chromatin structures
, RNA polymerase synthesizes RNA
RNA polymerase, just like DNA polymerase, can only synthesize 5' to 3' & read 3' to 5'
- has its own helicase domain, makes P.D. bond, doesn't require primer, cleaves
phosphate to use its energy
RNA vs DNA polymerases
DNA polymerase: synthesized 5' to 3', read 3' to 5', requires RNA or DNA primer, has a
3' to 5' exonuclease proofreading activity
RNA polymerase: synthesized 5' to 3', read 3' to 5', does not require a primer, does not
have any proofreading activity because RNA is not a permanent molecule, so quality
control is less stringent
RNA Polymerase I
transcribe and visit RNA only genes- not made into proteins (functional RNA); enzyme
that transcribes ribosomal RNA (rRNA) and is essential for protein translation
RNA Polymerase II
main one we talk about, "central dogma"- makes mRNA; all protein-coding genes
RNA Polymerase III
visit RNA only genes- functional pol. that is not made into proteins; tRNA genes, 5S
rRNA genes, some snRNA genes, and genes for other small RNAs
Promoters indicate transcription start points
promoters are double stranded and they are the four distinct DNA sequences arranged
near each other close to the start of the gene
- most transcriptional start sites only have 2 or 3 of the consensus sequences above
- promoter order from left to right: BRE (-35: 35 nucleotides away from start site), TATA
(-30), INR, DPE (+30)
- INR and DPE can become RNA
- these promoters are important because RNA polymerase can't land on a gene by itself
- +1 in front of the INR means that it is the first RNA nucleotide of the transcript that is
made into RNA
- -1 behind the INR means that it is not made into RNA
Transcription start site
precise DNA nucleotide that is turned into the first RNA nucleotide by RNA polymerase
Transcription factors
position RNA polymerase at the correct DNA sequence where transcription is supposed
to begin, and help to initiate transcription
- TFIID and TFIIH have many subunits (separate polypeptides that make it up) because
they do a ton of work
Transcription initiation
Process:
- TFIID (most important TF for identifying a gene) binds TATA box (or another
consensus sequence, if TATA is not there) and when it binds to the promoter, it will
bend it to attract other transcription factors
- bending the promoter attracts TFIIB which checks TFIID's work by making sure that
the right gene is turned on because if it is the wrong gene that can be a critical mistake
- TFIIB binds TFIID if it is in the right spot and it looks for BRE
- Once TFIIB & TFIID are in agreement, they bring in RNA polymerase (inactive form-
positioned at the promoter but not on yet) and other transcription factors
