Chapter 17: Transcription and Translation
Taking into account the wobble hypothesis, which of the following mRNA sequences could be bound to the tRNA anticodon 3′ GGC 5′? 3′ CCG 5′ 5′ UGC 3′ 5′ CCA 3′ 3′ UGC 5′
5′ CCA 3′
A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3'(mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. The anticodon loop of the first tRNA that will complement this mRNA is 5' ACG 3' 5' GGC 3' 3' UGC 5 '3' GGC 5' 5' UGC 3'
'3' GGC 5'
During transcription, in which direction is (1) RNA synthesized and in which direction is (2) the DNA template "read"? See Section 17.1 (Page) . View Available Hint(s) (1) 3'—>5' (2) 3'—>5' (1) 3'—>5' (2) 5'—>3' (1) 5'—>3' (2) 3'—>5' (1) 5'—>3' (2) 5'—>3'
(1) 5'—>3' (2) 3'—>5'
Put the following events of elongation in prokaryotic translation in chronological order. 1. Binding of mRNA with small ribosomal subunit 2. Recognition of initiation codon 3. Complementary base pairing between initiator codon and anticodon of initiator tRNA 4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. Attachment of the large subunit 1, 2, 3, 4, 5 1, 2, 3, 5, 4 2, 1, 4, 3, 5 5, 4, 3, 2, 1
1, 2, 3, 5, 4
If the sequence in the coding strand of DNA for a particular amino acid is 5'AGT3', then the anticodon on the corresponding tRNA would be ________. 5'UCA3' 5'ACU3' 5'AGU3' 5'TCA3'
5'ACU3'
Put the following events of transcription in chronological order.1. Sigma binds to the promoter region.2. The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands.3. Sigma binds to RNA polymerase.4. Sigma is released.5. Transcription begins. 3, 2, 1, 4, 5 2, 3, 1, 4, 5 2, 3, 4, 5, 1 3, 1, 2, 5, 4
3, 1, 2, 5, 4
Which of the following best describes the spliceosome? Three hundred different proteins make up a complex that splices out exons. A complex molecular machine that splices introns out of pre-mRNA Formed by snRNPs—splices out poly(A) tail once transcription is complete A complex molecular machine that splices exons out of pre-mRNA
A complex molecular machine that splices introns out of pre-mRNA
Which of the following statements about mutations is false? View Available Hint(s) A deletion mutation results in the loss of a base in the DNA sequence. An addition mutation results in an added base in the DNA sequence. Addition and deletion mutations disrupt the primary structure of proteins. A knock-out mutation results in a total absence of the mutated protein.
A knock-out mutation results in a total absence of the mutated protein.
If there were a mutation in a ribosome that prevented tRNA molecules from moving into the E site, how many amino acids would be found in the resulting peptide chain formed on this ribosome? A minimum of two A maximum of two A maximum of one None
A maximum of two
How does the arrival of a termination codon at the A site trigger the end of protein synthesis? See Section 17.5 (Page) . A special release tRNA binds at the A site and releases the polypeptide from the final tRNA to which it is bound. A protein release factor binds in the A site and releases the polypeptide from the final tRNA to which it is bound. The mRNA itself catalyzes the release of the polypeptide from the last tRNA. When the stop codon is reached, the ribosomal subunits separate and the mRNA and polypeptide are released.
A protein release factor binds in the A site and releases the polypeptide from the final tRNA to which it is bound.
During elongation, which site in the ribosome represents the location where a codon is being read? E site A site P site the small ribosomal subunit
A site
Transcription begins at a promoter. What is a promoter? View Available Hint(s) A site in DNA that recruits the RNA Polymerase Part of the RNA molecule itself A site found on the RNA polymerase The same as a start codon
A site in DNA that recruits the RNA Polymerase
elongation phase
A site is empty. the new aminoacyl tRNA binds to the A site. allows foe the situation of the second aa in the chain next the rRNA catalyze the creation of a peptide bond between the two amino acids also the covalent bond attached between the tRNA and the aa is broken now aa connected to tRNA in A site and not P site translocation (ribosome moves 3 base pairs over towards 3' end) tRNA in P site goes to E site tRNA in A site goes to P site A site is now empty new aminoacyl tRNA comp to mrna codon is added to the A site....
Which of the following statements about translational initiation in bacteria is true? The aminoacyl-tRNA anticodon first interacts with the codon in the mRNA, and then the complex binds to the small ribosomal subunit. A specific sequence on the large ribosomal subunit binds a complementary sequence on the mRNA. A specific sequence on the small ribosomal subunit binds a complementary sequence on the mRNA. Translation is initiated by the binding of the entire ribosome to the mRNA.
A specific sequence on the small ribosomal subunit binds a complementary sequence on the mRNA.
How does termination of translation take place? The 5' cap is reached. A stop codon is reached. The poly-A tail is reached. The end of the mRNA molecule is reached.
A stop codon is reached.
At which site do new aminoacyl tRNAs enter the ribosome during elongation? View Available Hint(s) A-site P-site E-site B-site
A-site
The micrograph in Figure 17.5a shows a DNA-mRNA hybrid. If the noncoding regions of the gene did not exist, what would the micrograph look like? See Section 17.2 (Page) . View Available Hint(s) Some, but not all, of the loops would be missing. All of the loops would be missing. There would be additional loops. There would be the same number of loops, but they would be smaller.
All of the loops would be missing.
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred? View Available Hint(s) An addition mutation and a deletion mutation. A deletion mutation. An addition mutation None.
An addition mutation and a deletion mutation.
Which of the following statements about transcription in bacteria and eukaryotes is true? Transcription in bacteria proceeds in the 3′ to 5′ direction, and transcription in eukaryotes occurs in the 5′ to 3′ direction. Transcription in bacteria proceeds in the 5′ to 3′ direction, and transcription in eukaryotes occurs in the 3′ to 5′ direction. Bacteria and eukaryotes rely on sigma proteins to initiate transcription. Bacteria and eukaryotes rely on proteins that recognize specific DNA sequences in the promoter to initiate transcription.
Bacteria and eukaryotes rely on proteins that recognize specific DNA sequences in the promoter to initiate transcription.
What determines which base is to be added to an RNA strand during transcription? View Available Hint(s) Base pairing between the DNA template strand and the RNA nucleotides The order of the chemical groups in the backbone of the RNA molecule Base pairing between the two DNA strands The previous base
Base pairing between the DNA template strand and the RNA nucleotides
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____. CAG CTG GAC CUG TCG
CUG
Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare? Codons are a nearly universal language among all organisms. Prokaryotic codons usually specify different amino acids than those of eukaryotes. Prokaryotic codons usually contain different bases than those of eukaryotes. The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes.
Codons are a nearly universal language among all organisms.
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand? View Available Hint(s) Complementary Covalently bound Permanently base-paired Identical
Complementary
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred? View Available Hint(s) None. Addition. Both addition and deletion. Deletion.
Deletion.
True or false? A codon is a group of three bases that can specify more than one amino acid. View Available Hint(s) True False
False
transcription is synthesis of RNA from a DNA template
For example: DNA coding strand 5' ATCGA 3" DNA template 3' TAGCT 5' RNA template 5' AUCGA 3' coding and RNA template are almost identical, expect RNA has U instead of T H bonds form between the nitrogenous bases
transcription looks a like like DNA synthesis
H bond form between complementary strands subunits added are NTP's (3 phoshpates...) phosphodiester bond formed between 5' phosphate and 3' OH of the previous nucelotide) only goes 5' to 3' USES RNA POLYMERASE
How is a mutation in a bacterial cell that deletes three base pairs 10 base pairs upstream from the +1 site likely to affect transcription and why? See Section 17.1 (Page) . View Available Hint(s) .Initiation will be inhibited because RNA polymerase core enzyme cannot bind to the promoter. Initiation will be inhibited because sigma cannot bind to the promoter. Termination will not occur because hairpin secondary structure cannot form. A three-base-pair deletion is too small to have an effect.
Initiation will be inhibited because sigma cannot bind to the promoter
what is the function of the ACC sequence at the 3' end? It stabilizes the tRNA-amino acid complex. It attaches to an amino acid. It base pairs with the codon of mRNA. It is the active site of this ribozyme.
It attaches to an amino acid.
what is the function of the ACC sequence at the 5' end? It stabilizes the tRNA-amino acid complex. It attaches to an amino acid. It base pairs with the codon of mRNA. It is the active site of this ribozyme.
It base pairs with the codon of mRNA.
What happens to RNA polymerase II after it has completed transcription of a gene? View Available Hint(s) It is free to bind to another promoter and begin transcription. It begins transcribing the next gene on the chromosome. It joins with another RNA polymerase to carry out transcription. It is degraded.
It is free to bind to another promoter and begin transcription.
The nucleotide shown below is called cordycepin triphosphate. It is a natural product of a fungus that is used in traditional medicines. If cordycepin triphosphate is added to a cell-free transcription reaction, the nucleotide is added onto the growing RNA chain but no more nucleotides can then be added. The added cordycepin is always found at the 3' end of an RNA. Examine the structure of cordycepin and explain why it ends transcription. It lacks a 3' OH. It lacks a 5' OH. It prevents the association of RNA polymerase and sigma. It cannot be recognized by RNA polymerase.
It lacks a 3' OH.
During translation, nucleotide base triplets (codons) in mRNA are read in sequence in the 5' → 3' direction along the mRNA. Amino acids are specified by the string of codons. What amino acid sequence does the following mRNA nucleotide sequence specify? 5′−AUGGCAAGAAAA−3′5′−AUGGCAAGAAAA−3′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-Thr-Lys-Gly).
Met-Ala-Arg-Lys
What amino acid sequence does the following DNA nucleotide sequence specify? 3′−TACAGAACGGTA−5′3′−TACAGAACGGTA−5′
Met-Ser-Cys-His
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)? View Available Hint(s) One deletion mutation. One addition and two deletion mutations. One addition and one deletion mutation. One addition mutation.
One addition and one deletion mutation.
DNA does not store the information to synthesize which of the following? View Available Hint(s) Messenger RNA DNA Proteins Organelles
Organelles
The initiator tRNA attaches at the ribosome's _____ site. A translocation E P Q
P
Which of the following processes is an example of a post-translational modification? View Available Hint(s) Phosphorylation Initiation Peptide bond formation Elongation
Phosphorylation
holoenzyme (bacteria)
RNA polymerase and sigma bind to form the holoenzyme. that complex then binds to the promoter region of the DNA. Sigma recognizes where the complex must bind to the DNA for RNA polymerase to start transcription in the right spot
Which of the following features is a significant difference in the function of DNA polymerases versus RNA polymerases? See Section 17.1 (Page) . Only RNA polymerase adds nucleotide precursors (dNTPs) to a growing chain. RNA polymerase, but not DNA polymerase, is an enzyme. RNA polymerase does not require a primer to add new nucleotides. DNA polymerase extends the growing chain in the 5' to 3' direction, whereas RNA polymerase extends growing chains from 3' to 5'.
RNA polymerase does not require a primer to add new nucleotides.
Which of the following steps occurs last in the initiation phase of translation? View Available Hint(s) The small subunit of the ribosome binds to the 5' cap on the mRNA. A peptide bond is formed between two adjacent amino acids. The large ribosomal subunit joins the complex. An aminoacyl tRNA binds to the start codon.
The large ribosomal subunit joins the complex.
During elongation, what substrates are used for the polymerization reaction catalyzed by RNA polymerase? Deoxyribonucleoside triphosphates (dNTPs) Ribonucleoside triphosphates (NTPs) Small nuclear ribonucleoproteins (snRNPs)
Ribonucleoside triphosphates (NTPs)
Where does translation take place? View Available Hint(s) Golgi apparatus Endoplasmic reticulum Nucleus Ribosome
Ribosome
What is the first step during the initiation of translation? An aminoacyl tRNA binds to the codon in the A site on the ribosome Ribosome binding site on the mRNA binds to a complementary sequence of rRNA on the ribosome small subunit Ribosome large subunit binds to the ribosome small subunit An initiator aminoacyl tRNA binds to the start codon on the mRNA
Ribosome binding site on the mRNA binds to a complementary sequence of rRNA on the ribosome small subunit
What is the function of the sigma subunit of RNA polymerase in bacterial transcription? See Section 17.1 (Page) . Sigma provides the RNA primer onto which RNA polymerase adds new dNTP subunits. Sigma is the portion of the enzyme that recognizes specific sequences in the promoter. Sigma recognizes the transcriptional termination signal. Sigma carries out the elongation of the new RNA from 5' to 3'.
Sigma is the portion of the enzyme that recognizes specific sequences in the promoter.
An aminoacyl-tRNA that enters the A site of the ribosome will next occupy which site? See Section 17.5 (Page) . No site; the A site is the last place the tRNA occupies before it leaves the complex. The large subunit of the ribosome c The E site
The P site
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find? The molecule is digested by enzymes because it is not protected at the 5' end. The mRNA attaches to a ribosome and is translated, but more slowly. The mRNA is quickly converted into a ribosomal subunit. The cell adds a new poly-A tail to the mRNA.
The molecule is digested by enzymes because it is not protected at the 5' end.
Which of the following statements best describes the promoter of a protein-coding gene? View Available Hint(s) The promoter is part of the RNA molecule itself. The promoter is a site found on RNA polymerase. The promoter is a nontranscribed region of a gene. The promoter is a site at which only RNA polymerase will bind.
The promoter is a nontranscribed region of a gene.
What is meant by translocation? View Available Hint(s) The ribosome slides one codon down the mRNA. The completed polypeptide is released from the ribosome. The two ribosomal subunits are joined in a complex. The polypeptide chain grows by one amino acid.
The ribosome slides one codon down the mRNA.
How are RNA hairpin turns related to termination in E. coli? A three-base repeat signals a stop sequence, and the RNA transcript is released. The hairpin turn prevents more nucleoside triphosphates from entering the active site of the enzymes, effectively shutting off the process of polymerization. Release factors bind to sites on the hairpin turn, causing release of the RNA transcript. The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.
The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.
What is the reaction catalyzed by aminoacyl-tRNA synthetases that is essential for translation? View Available Hint(s) These enzymes catalyze formation of the bonds between the tRNA and the appropriate amino acids. These enzymes catalyze the formation of tRNAs. These enzymes modify the mRNA into its mature form. These enzymes carry out synthesis of new proteins, joining amino acids via peptide bonds.
These enzymes catalyze formation of the bonds between the tRNA and the appropriate amino acids.
What is the process called that converts the genetic information stored in DNA to an RNA copy? View Available Hint(s) Translation Translocation Transcription Replication
Transcription
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein? View Available Hint(s) Two. None. Three. One.
Two.
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____. UUA TTT AAA UUU
UUU
Termination of transcription in bacteria occurs when ________. large and small subunits of the RNA polymerase dissociate a deoxyribonucleotide is base-paired to the 3' end of the transcript, signaling completion the 5' cap structure on the nascent (new) RNA molecule loops back and interferes with RNA polymerase a hairpin secondary structure forms in the RNA transcript, and it separates from the RNA polymerase
a hairpin secondary structure forms in the RNA transcript, and it separates from the RNA polymerase
During RNA processing a(n) _____ is added to the 3' end of the RNA. .3' untranslated region a long string of adenine nucleotides 5' untranslated region coding segment modified guanine nucleotide
a long string of adenine nucleotides
What enzyme catalyzes the attachment of an amino acid to tRNA? aminoacyl-tRNA synthetase rubisco dextrinase argininosuccinate lyase nuclease
aminoacyl-tRNA
A ribozyme is _____. an enzyme that catalyzes the association between the large and small ribosomal subunit san enzyme that synthesizes RNA as part of the transcription process an RNA with catalytic activity a catalyst that uses RNA as a substrate an enzyme that synthesizes RNA primers during DNA replication
an RNA with catalytic activity
polyribosomes
bacteria and eukaryotes multiple ribosomes on a single mRNA transcript (efficiency) ribosome closer to the 3' end, polypeptide chain is longer ribosome closer to the 5' end, polypeptide chain is shorter
bacteria vs eukaryotes
bacteria: only one RNA polymerase promoter structure -35 and -10 box proteins that associate with it: sigma RNA processing: rare eukaryotes: three different RNA polymerases promoter structure: TATA box proteins: many (chapter 19) RNA processing: extensive (5' cap, 3' PolyA tail, alt splicing, splicing)
Ribosomes can attach to prokaryotic messenger RNA _____. once replication is complete once the primary transcript has been released from RNA polymerase before transcription is complete once post-transcriptional modification is complete
before transcription is complete
Translation occurs in the _____. cytoplasm lysosome nucleus Golgi apparatus nucleoplasm
cytoplasm
David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). These two regions of the promoter _____. signal the initiation site separate the two DNA strands attach the correct nucleotide triphosphate to the template DNA strand bind the sigma subunit that is associated with RNA polymerase
bind the sigma subunit that is associated with RNA polymerase
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____. binding of the anticodon to small subunit of the ribosome shape of the A and P sites of ribosomes attachment of amino acids to rRNAs binding of ribosomes to mRNA binding of the anticodon to the codon and the attachment of amino acids to tRNAs
binding of the anticodon to the codon and the attachment of amino acids to tRNAs
The anticodon of a particular tRNA molecule is _____. complementary to the corresponding triplet in rRNA complementary to the corresponding mRNA codon changeable, depending on the amino acid that attaches to the tRNA catalytic, making the tRNA a ribozyme the part of tRNA that bonds to a specific amino acid
complementary to the corresponding mRNA codon
Which of the following occurs in prokaryotes but not in eukaryotes? translation in the absence of a ribosome post-transcriptional splicing gene regulation concurrent transcription and translation
concurrent transcription and translation
The RNA segments joined to one another by spliceosomes are _____. caps exons snRNPs tails introns
exons
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.
false (no tRNAs comp to three stop codons. codes for a release factor)
post translational modification
folding, activation/degradation, phosphorylation, etc
The poly(A) tail at the end of eukaryotic mRNA __________. allows ribosomes to initiate translation at the 3′ end of the mRNA helps protect the mRNA from degradation by enzymes in the cytoplasm codes for the hydrolysis of the RNA polymerase adds the 5′ cap to the end of mRNA
helps protect the mRNA from degradation by enzymes in the cytoplasm
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure above? covalent bonding between sulfur atoms van der Waals interactions between hydrogen atoms ionic bonding between phosphates hydrogen bonding between base pairs peptide bonding between amino acids
hydrogen bonding between base pairs
role of tRNA in translation
hypothesis: mRNA interacts directly with amino acids know that nitrogenous bases form H bonds so many some preferential H bonds between mRNA codons and specific amino acids problem: some amino acids do not form H bonds and how would the H bonds make specific binding happen (what would prevent proline from binding where met goes?) hypothesis 2: adapter molecule interacts with mRNA and holds the amino acids this one was correct adapter molecules bind to mRNA via complementary base pairing rules and bring with it the correct amino acid to be positioned in correct place in ribosome to be added to the polypeptide chain
introns are spliced out of the original mRNa
introns do not code for anything. they are transcribed but spliced out by spliceosomes (they connect the exons) mature mRNA that leaves nucleus lacks introns
What does a bacterial RNA polymerase produce when it transcribes a protein-coding gene? rRNA snRNA tRNA mRNA
mRNA
Which nucleic acid is translated to make a protein? View Available Hint(s) DNA tRNA mRNA rRNA
mRNA
Translation requires _____. mRNA, DNA, and rRNA mRNA, tRNA, DNA, and rRNA mRNA, tRNA, and DNA mRNA, tRNA, and rRNA
mRNA, tRNA, and rRNA
eukaryotes are given a cap and tail
modified 5' guanine cap and 3' poly A tail also a 5' and 3' untranslated region bacteria and eukaryotes both have the 5' and 3' untranslated region
During RNA processing a(n) _____ is added to the 5' end of the RNA. .3' untranslated region a long string of adenine nucleotides 5' untranslated region coding segment modified guanine nucleotide
modified guanine nucleotide
According to the wobble hypothesis, __________. more than one codon codes for an amino acid, and they tend to have the same nucleotides in all three positions more than one codon codes for an amino acid, and they tend to have the same nucleotides at the first and third positions more than one codon codes for an amino acid, and they tend to have different nucleotides in all three positions more than one codon codes for an amino acid, and they tend to have different nucleotides in the first two positions
more than one codon codes for an amino acid, and they tend to have different nucleotides in the first two positions
The following eukaryotic structural gene contains two introns and three exons. exon 1 intron 1 exon 2 intron 2 exon 3 The table below shows four possible mRNA products of this gene. Use the labels to explain what mutation(s) may have resulted in each mRNA. exon 1 exon 2 intron 2 exon 3 no mRNA produced exon 1 intron 1 exon 2 intron 2 exon 3 exon 1 exon 2 exon 3
mutation in splicing intron 2 mutation in promoter sequence mutation in splicing intron 1 and 2 no mutation
DNA and mRNa hybrids are made in eukaryotes. do they match up perfectly?
no, the mRNA transcript is shorter than the DNA because there are regions that get cut out of the mRNA (introns) match up perfectly in bacteria bc bacteria does not produce introns (specific to eukaryotes)
A promoter and a start codon are similar in that both are sequences of ________that are required to start important processes, and both determine the sites where the process will begin. The key differences are that the promoter is needed to start _______and the start codon is needed to start _____ . Also, the promoter is a _______only, and the start codon is a sequence found within a(n)_______.
nucleic acids transcription translation DNA sequence mRNA
The mRNA is smaller than the length of the DNA that codes for it because ________. post-transcriptional modification removes the introns post-transcriptional modification removes the exons bases are added to the tail of the primary transcript the regulatory regions (exons) of the gene are not transcribed
post-transcriptional modification removes the introns
why add the cap and tail?
prevent the mRNA from degradation
A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that _____. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU the ribosome will skip a codon every time a UUU is encountered the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons none of the proteins in the cell will contain phenylalanine
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU
what part of the promoter does sigma recognize and bind to?
recognized -35 box and -10 box. (ab 35 and 10 nucleotides away from the start site respectively) located upstream of the DNA that will be transcribed promoter is NOT a template for transcription but a landing spot for RNA polymerase
how does amino acyl tRNA synthetase place the right amino acid on their respective tRNA?
recognizes the shape of the tRNA and binds to some spots like the anticodon tRNA complementary to the mRNA
initiation phase of translation
ribosome binding site. mRNA complementary base pairs to a sequence of rRNA within the small subunit of the ribosome also initiation factors binds in such a way where the met codon is in the P site when the whole ribosome assembles anticodon on aminoacyl tRNA comp binds with the codon in the mRNA large ribosomal subunit is added initiation is finished
transcription and translation occur simultaneously in bacteria
ribosome translates mRNa as it is being synthesized from the DNA template the more ribosomes there are, the closer to the 3' end of the mRNA you are therefore you are closer to the 5' end of the template strand of DNA this can happen bc not a separation in location between DNA template and proteins like in eukaryotes also don't require the processing (splicing) that occurs in eukaryotes ribosomes attach to the 5' end of the mRNA transcript this is just a way of increasing efficiency
What molecules in the spliceosome catalyze the intron removal reactions? RNA polymerases tRNA introns ribozymes
ribozymes
steps involved in transcription
rna polymerase is able to separate the double stranded DNA helix by itself (does not need helicase) can also add NTPs de nuovo, does not need an existing strand to extend (unlike DNA polymerase) RNA polymerase starts to create the complementary strand using NTPs (5'-3') once transcription beings, sigma dissociates as it is no longer needed. can go form another holoenzyme elsewhere. ending transcription in bacteria: a secondary structure forms (hairpin) which causes RNA polymerase to destabilize and fall off the DNA template strand. hairpin forms because of internal complementarity all separate from one another and now you have a mRNA
Spliceosomes are composed of _____. small RNAs and proteins polymerases and ligases introns and exons the RNA transcript and protein
small RNAs and proteins
the structure of a ribosome during translation
small subunit large subunit E P and A site moves from 5' to 3'
snRNPs edit the mRNa within the nucleus
spliceosome-ribozyme (molecule with catalytic properties) removes introns composed of multiple snRNPs composed of small snRNA and proteins snRNA is the ribozyme snRNPs assemble at points on intron/exons boarders snRNA catalyze the splicing
termination
stop codon is read causing a release factor to enter the A site (protein) catalyzes the breakage of the last covalent bond holding the polypeptide chain to the tRNA in the P site once the bond is broken the entire complex falls apart
Transcription
synthesis of RNA from a DNA template during transcription, only one strand of the DNA is read to produce a complementary RNA strand. the other strand is just ignored. newly made RNA and DNa are complementary and antiparallel strand used as template: template strand other strand: non-template/coding strand
name of the adapter molecule: tRNA secondary structure of aminoacyl tRNA
t shape. loops where unpaired bases. stems where internal complementarity. 3' end contains the amino acid. anticodon is at the bottom most loop and contains the sequence that complementary base pairs to the mRNA codon tRNA covalently bound to an amino acid is called a charged tRNA or an aminoacyl tRNA (happens bc of aminoacyl tRNA synthetase)
There should be a strong positive correlation between the rate of protein synthesis and _____. the quantity of RNA polymerase the size of mRNA the number of ribosomes the quantity of DNA polymerase
the number of ribosomes
Once a peptide bond has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next? reading of the next codon of mRNA initiation breaking the codonanticodon hydrogen bonds holding the tRNA in the A site translocation
translocation
wobble
violation of rules between complementary base pairing between codon and anticodon allow for there to be less tRNAs than codons present the third base pair of the codon in the mRNA is allowed to not exactly complementary base pair with the anticodon ex: tRNa can recognize the codons UCCC and UCU and will comp base pair its anticodon of AGG to it even tho it violates comp rules. both code for serine