Genetics Exam 1: MasteringGenetics HW Study Questions
Which of the following are classified as functional or structural RNAs? A) mRNAs and tRNAs B) tRNAs, rRNAs, and snRNAs C) Only mRNAs D) mRNAs, tRNAs, and rRNAs
...B) tRNAs, rRNAs, and snRNAs
1) DNA helicase does what? 2) Single-stranded binding proteins? 3) Primase? 4) Topoisomerase?
1) DNA helicase breaks the hydrogen bonds between DNA strands, separating them. 2) Single-stranded binding proteins bind to the single-stranded DNA and prevent it from reannealing. 3) Primase synthesizes a short RNA primer that is necessary for DNA polymerase III to begin synthesizing DNA. 4) Topoisomerase relieves the supercoiling caused by unwinding the DNA
Determine which of the following sequences and structures represent part of mature eukaryotic mRNA. Check all that apply. -5'-cap -start codon -promoter -AAUAAA -intron -poly-A tail -termination sequence -stop codon -5'-UTR -3'-UTR
-5'-cap -start codon -AAUAAA -poly-A tail -stop codon -5'-UTR -3'-UTR
After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus? -Coding sequences called exons are spliced out by ribosomes. -A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. -A translation stop codon is added at the 3' end of the pre-mRNA. -Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. -A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
-A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. -Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. -A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
Which of the following best describe(s) the function of the 5'mRNA cap? Check all that apply. -To provide a binding site for poly(A) polymerase -To protect the transcript from degradation -It provides a site for ribosome binding in the cytoplasm. -Termination of transcription
-To protect the transcript from degradation -It provides a site for ribosome binding in the cytoplasm. The 5' cap is essential for recognition of the mRNA by ribosomes in the cytoplasm.
1) DNA polymerase III does what? 2) DNA polymerase I? 3) DNA ligase?
1) DNA polymerase III synthesizes most of the DNA during DNA replication. 2) DNA polymerase I removes the RNA primers and replaces them with DNA. 3) DNA ligase forms a phosphodiester bond in the DNA backbone to fill in the nicks left there from removing the RNA primers.
What is the complementary DNA sequence to 5′ ATGCTTGACTG 3′?
5′ CAGTCAAGCAT 3′
In a DNA nucleotide, to which carbon on deoxyribose is the nitrogenous base attached? A) 1′ B) 2′ C) 3′ D) 5′
A) 1'
In 1928, Frederick Griffith conducted a series of experiments that demonstrated which of the following? A) A "transformation factor" could be released from one cell and picked up by another cell, thus changing the genetic identity of the recipient cell. B) DNA was localized to chromosomes. C) DNA was a polymer composed of four repeating nucleotides. D) Nuclei of white blood cells contain a weakly acidic substance, termed nuclein.
A) A "transformation factor" could be released from one cell and picked up by another cell, thus changing the genetic identity of the recipient cell.
Which of the following reagents is not required for the polymerase chain reaction? A) Dideoxynucleotide triphosphates B) A heat-stable DNA polymerase C) Deoxynucleotide triphosphates D) A pair of DNA primers
A) Dideoxynucleotide triphosphates Dideoxynucleotides terminate chain elongation due to the absence of a 3'-OH group, which is required for new nucleotide addition in the process of DNA replication. Dideoxynucleotides are used in DNA sequencing reactions.
Which of the following statements about DNA replication in E. coli is true? A) Replication proceeds in both directions from a single origin of replication. B) Replication proceeds in both directions from multiple origins of replication. C) Replication proceeds in one direction from a single origin of replication. D) Replication proceeds in one direction from multiple origins of replication.
A) Replication proceeds in both directions from a single origin of replication.
What is a charged tRNA? A) a tRNA that carries a specific amino acid B) a tRNA that is bound to an initiation factor (IF) C) a tRNA that is bound to the small ribosomal subunit D) an ionic form of a tRNA
A) a tRNA that carries a specific amino acid
Why are genes for rRNA and tRNA considered to be genes even though they do not produce polypeptides? A) rRNA and tRNA are also gene products along with polypeptides. B) The structures of tRNA and rRNA are similar to the structures of polypeptides. C) The functions of rRNA and tRNA are similar to the functions of polypeptides. D) The statement is false; DNA sequences encoding for rRNA and tRNA are not actually genes.
A) rRNA and tRNA are also gene products along with polypeptides.
At each replication fork, _______ moves along the parental DNA, separating the two strands by breaking the ________ bonds between the base pairs. (This makes the two parental DNA strands available to the DNA polymerases for replication.) As soon as the base pairs separate at the replication fork, _______________________ attach to the separated strands and prevent the parental strands from rejoining. As _______ separates the two parental strands, the parental DNA ahead of the replication fork becomes more tightly coiled. To relieve strain ahead of the replication fork, ____________ breaks a covalent bond in the sugar-phosphate backbone of one of the two parental strands. Breaking this bond allows the DNA to swivel around the corresponding bond in the other strand and relieves the strain caused by the unwinding of the DNA at the _________.
At each replication fork, helicase moves along the parental DNA, separating the two strands by breaking the hydrogen bonds between the base pairs. (This makes the two parental DNA strands available to the DNA polymerases for replication.) As soon as the base pairs separate at the replication fork, single-strand binding proteins attach to the separated strands and prevent the parental strands from rejoining. As helicase separates the two parental strands, the parental DNA ahead of the replication fork becomes more tightly coiled. To relieve strain ahead of the replication fork, topoisomerase breaks a covalent bond in the sugar-phosphate backbone of one of the two parental strands. Breaking this bond allows the DNA to swivel around the corresponding bond in the other strand and relieves the strain caused by the unwinding of the DNA at the helicase.
What normally binds to an open A-site on the ribosome? A) An empty tRNA after its amino acid has been added to the polypeptide chain B) A tRNA that carries the next amino acid to be added to the polypeptide chain C) The initiator tRNA that carries the first amino acid in the polypeptide chain D) The 3' UTR (untranslated region) of the mRNA
B) A tRNA that carries the next amino acid to be added to the polypeptide chain
Which of the following is characteristic of transcription in eukaryotes but not in prokaryotes? A) A single transcript may be transcribed and translated simultaneously. B) Exon splicing C) A 3' untranslated trailer sequence D) A 5' untranslated leader sequence
B) Exon splicing Introns must be removed from eukaryotic pre-mRNA; prokaryotic mRNA does not contain introns.
Which of the following lists steps of mRNA production in eukaryotes in the correct order? A) Transcription, 5' cap addition, addition of poly-A tail, passage through nuclear membrane, exon splicing B) Transcription, 5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane C) Transcription, addition of poly-A tail, 5' cap addition, exon splicing, passage through nuclear membrane D) 5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane, transcription
B) Transcription, 5' cap addition, addition of poly-A tail, exon splicing, passage through nuclear membrane
When a peptide bond is formed between two amino acids, one is attached to the tRNA occupying the P site and the other _______. A) is attached to the tRNA occupying the E site B) is attached to the tRNA occupying the A site C) is free in the cytoplasm D) is attached through hydrogen bonds to the mRNA
B) is attached to the tRNA occupying the A site
Bacterial transcription is a four-stage process. 1. __________________: RNA polymerase is a holoenzyme composed of a five-subunit core enzyme and a sigma (σ) subunit. Different types of σ subunits aid in the recognition of different forms of bacterial promoters. The bacterial promoter is located immediately upstream of the starting point of transcription (identified as the +1 nucleotide of the gene). The promoter includes two short sequences, the -10 and -35 consensus sequences, which are recognized by the σ subunit. 2. _________________: The RNA polymerase holoenzyme first binds loosely to the promoter sequence and then binds tightly to it to form the closed promoter complex. An open promoter complex is formed once approximately 18 bp of DNA around the -10 consensus sequence are unwound. The holoenzyme then initiates RNA synthesis at the +1 nucleotide of the template strand. 3. ____________________: The RNA-coding region is the portion of the gene that is transcribed into RNA. RNA polymerase synthesizes RNA in the 5′ → 3′ direction as it moves along the template strand of DNA. The nucleotide sequence of the RNA transcript is complementary to that of the template strand and the same as that of the coding (nontemplate) strand, except that the transcript contains U instead of T. 4. ____________________: Most bacterial genes have a pair of inverted repeats and a polyadenine sequence located downstream of the RNA-coding region. Transcription of the inverted repeats produces an RNA transcript that folds into a stem-loop structure. Transcription of the polyadenine sequence produces a poly-U sequence in the RNA transcript, which facilitates release of the transcript from the DNA.
Bacterial transcription is a four-stage process. 1. Promoter recognition: 2. Chain initiation: 3. Chain elongation: 4. Chain termination:
Once elongation is underway, tRNAs involved in the process occupy a series of sites on the complexed ribosome. The occupation of sites occurs in the following order. A) A Site, P Site, E Site, S Site B) A Site, S Site, E Site C) A Site, P Site, E Site D) P Site, E Site, A Site
C) A Site, P Site, E Site
What is a gene? A) A gene is an RNA, which codes for translation of a protein. B) A gene is the unit of heritage, mutation, recombination and function. C) A gene is a segment of DNA that contains the information for transcription of an RNA. D) A gene is a structural protein that defines a heritable trait.
C) A gene is a segment of DNA that contains the information for transcription of an RNA.
At which site does the charged initiator tRNA bind during protein synthesis? A) T site B) E site C) P site D) A site
C) P site The initiator tRNAfmet binds to the mRNA codon in the P site of the ribosome. The initiator tRNA is the only one that binds in the P site; all other tRNAs bind the ribosome in the A site.
Which of the following statements best describes the structure of RNA molecules in general? A) RNA molecules are single-stranded, but they commonly form localized secondary structures by forming covalent bonds between regions of the molecule. B) RNA molecules are single-stranded, and they do not commonly form localized secondary structures. C) RNA molecules are single-stranded, but they commonly form localized secondary structures by base pairing between regions of the molecule. D) RNA molecules form a double helix modeled after the DNA from which they are encoded.
C) RNA molecules are single-stranded, but they commonly form localized secondary structures by base pairing between regions of the molecule.
Which of the following best describes the first step in the formation of the translation initiation complex? A) The large ribosomal subunit binds to the small ribosomal subunit. B) The large ribosomal subunit binds to an mRNA sequence near the 5' end of the transcript C) The small ribosomal subunit binds to an mRNA sequence near the 5' end of the transcript D) The small ribosomal subunit binds to an mRNA sequence near the 3' end of the transcript.
C) The small ribosomal subunit binds to an mRNA sequence near the 5' end of the transcript
In prokaryotes, the methionine that initiates the formation of a polypeptide chain differs from subsequently added methionines in that _______. A) incorporation of the initial methionine does not require a tRNA B) its tRNA anticodon is not complementary to the AUG codon C) a formyl group is attached to the initiating methionine D) the initiating methionine is not an amino acid
C) a formyl group is attached to the initiating methionine
What event occurs during translocation? A) Amino acids are added to the polypeptide chain. B) The polypeptide is cleaved from the terminal tRNA. C) mRNA shifts in the 5' direction along the ribosome. D) The two ribosomal subunits join to form a complex.
C) mRNA shifts in the 5' direction along the ribosome.
Below is the sequence of the coding strand of DNA that flanks the coding region of the GFP gene. Diagram of the DNA coding strand with this sequence: 5'-ATCGG--GFP gene--TTAGAC-3' Select the sequence of the forward primer that you would use to amplify the GFP gene using PCR. Remember that the forward primer hybridizes to the template strand of DNA. A) 5' GTCTAA 3' B) 5' TAGCCC 3' C) 5' TTAGAC 3' D) 5' ATCGGG 3' Now, select the sequence for the reverse primer that you would use to amplify the GFP gene shown in Part C. Remember that the reverse primer hybridizes to the coding strand of DNA. A) 5' GTCTAA 3' B) 5' TAGCCC 3' C) 5' ATCGGG 3' D) 5' TTAGAC 3'
D) 5' ATCGGG 3' A) 5' GTCTAA 3'
Which of the following statements about DNA structure is true? A) Nucleic acids are formed through phosphodiester bonds that link nucleosides together. B) The pentose sugar in DNA is ribose. C) Hydrogen bonds formed between the sugar‑phosphate backbones of the two DNA chains help to stabilize DNA structure. D) The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
D) The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
Translation is directly dependent on all of the following associations except _______. A) complementary base pairing between mRNA and rRNA B) complementary base pairing between mRNA and tRNA C) association of the 30S and the 50S ribosomal subunits D) complementary base pairing between mRNA and DNA
D) complementary base pairing between mRNA and DNA
DNA polymerase ___ can only add nucleotides to the 3' end of a new DNA strand. Because the two parental DNA strands of a double helix are __________ (go from 3' to 5' in opposite directions), the direction that DNA pol ___ moves on each strand emerging from a single replication fork must also be opposite. For example, in the replication fork on the left, the new strand on top is being synthesized from 5' to 3', and therefore DNA pol ___ moves away from the replication fork. Similarly, the new strand on the bottom of that same replication fork is being synthesized from 5' to 3'. But because the bottom parental strand is running in the opposite direction of the top parental strand, DNA pol ___ moves toward the replication fork. In summary, at a single replication fork, one strand is synthesized away from the replication fork, and one strand is synthesized toward the replication fork. When you look at both replication forks, note that a single new strand is built in the same direction on both sides of the replication bubble.
DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand. Because the two parental DNA strands of a double helix are antiparallel (go from 3' to 5' in opposite directions), the direction that DNA pol III moves on each strand emerging from a single replication fork must also be opposite. For example, in the replication fork on the left, the new strand on top is being synthesized from 5' to 3', and therefore DNA pol III moves away from the replication fork. Similarly, the new strand on the bottom of that same replication fork is being synthesized from 5' to 3'. But because the bottom parental strand is running in the opposite direction of the top parental strand, DNA pol III moves toward the replication fork. In summary, at a single replication fork, one strand is synthesized away from the replication fork, and one strand is synthesized toward the replication fork. When you look at both replication forks, note that a single new strand is built in the same direction on both sides of the replication bubble.
During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. Which of the following initially determines which DNA strand is the template strand, and therefore in which direction RNA polymerase II moves along the DNA? A) the location along the chromosome where the double-stranded DNA unwinds B) the position of the gene's promoter on the chromosome C) the location of specific proteins (transcription factors) that bind to the DNA D) which of the two strands of DNA carries the RNA primer E) the specific sequence of bases along the DNA strands
E) the specific sequence of bases along the DNA strands
A standard PCR cycle includes three steps: denaturation (95°C), annealing (55°C), and elongation (65°C). Drag each ingredients of a PCR reaction into the bin labeled with the step in the PCR cycle in which it is first used. Denaturation (95C) uses what? Annealing? Elongation?
Denaturation: DNA Template Annealing: Primers Elongation: Taq polymerase and dNTPs During the denaturation step of a PCR cycle, the template DNA strands are separated or denatured. Next, during the annealing step, the single-stranded primers hybridize to the denatured DNA template. Finally, during the elongation step, Taq polymerase synthesizes a new strand of DNA from the DNA template in a 5' to 3' direction, starting at the 3' end of the primers, by adding dNTPs to the 3' end of the new DNA strand.
The enzyme EF‑Tu catalyzes the formation of a peptide bond between the amino acid held by the tRNA in the A site and the elongating amino acid chain held by the tRNA in the P site. True or False.
False Peptidyl transferase is the enzyme that catalyzes the formation of peptide bonds during translation. EF‑Tu is an elongation factor that facilitates the entry of charged tRNAs into the A site.
WHAT is the one word that fills in all the blanks (as in, every blank contains the same word). In eukaryotes, binding of RNA polymerase II to DNA involves several other proteins known as __________________. Many of these _______________________ bind to the DNA in the promoter region (shown below in green), located at the 3' end of the sequence on the template strand. Although some _____________________ bind to both strands of the DNA, others bind specifically to only one of the strands. __________________ do not bind randomly to the DNA. Information about where each ________________ binds originates in the base sequence to which each __________________ binds. The positioning of the ________________ in the promoter region determines how the RNA polymerase II binds to the DNA and in which direction transcription will occur.
In eukaryotes, binding of RNA polymerase II to DNA involves several other proteins known as transcription factors. Many of these transcription factors bind to the DNA in the promoter region (shown below in green), located at the 3' end of the sequence on the template strand. Although some transcription factors bind to both strands of the DNA, others bind specifically to only one of the strands. Transcription factors do not bind randomly to the DNA. Information about where each transcription factor binds originates in the base sequence to which each transcription factor binds. The positioning of the transcription factors in the promoter region determines how the RNA polymerase II binds to the DNA and in which direction transcription will occur.
Is coupling of transcription and translation possible in single-celled eukaryotes such as yeast? YES or NO.
No.
Once RNA polymerase II is bound to the promoter region of a gene, transcription of the template strand begins. As transcription proceeds, three key steps occur on the RNA transcript: Early in transcription, when the growing transcript is about 20 to 40 nucleotides long, a modified guanine nucleotide is added to the 5' end of the transcript, creating a 5' _____. _______ are spliced out of the RNA transcript by __________, and the ________ are joined together, producing a continuous coding region. A ______ tail (between 50 and 250 adenine nucleotides) is added to the 3' end of the RNA transcript. Only after all these steps have taken place is the mRNA complete and capable of exiting the nucleus. Once in the cytoplasm, the mRNA can participate in translation.
Once RNA polymerase II is bound to the promoter region of a gene, transcription of the template strand begins. As transcription proceeds, three key steps occur on the RNA transcript: Early in transcription, when the growing transcript is about 20 to 40 nucleotides long, a modified guanine nucleotide is added to the 5' end of the transcript, creating a 5' cap. Introns are spliced out of the RNA transcript by spliceosomes, and the exons are joined together, producing a continuous coding region. A poly-A tail (between 50 and 250 adenine nucleotides) is added to the 3' end of the RNA transcript. Only after all these steps have taken place is the mRNA complete and capable of exiting the nucleus. Once in the cytoplasm, the mRNA can participate in translation.
There are three principles to keep in mind when predicting the sequence of the mRNA produced by transcription of a particular DNA sequence. Info, not really a question.
The RNA polymerase reads the sequence of DNA bases from only one of the two strands of DNA: the template strand. The RNA polymerase reads the code from the template strand in the 3' to 5' direction and thus produces the mRNA strand in the 5' to 3' direction. In RNA, the base uracil (U) replaces the DNA base thymine (T). Thus the base-pairing rules in transcription are A→U, T→A, C→G, and G→C, where the first base is the coding base in the template strand of the DNA and the second base is the base that is added to the growing mRNA strand.
The RNA polymerase reads the template strand from the ______ direction, and synthesizes RNA from ______. The __________ strand is the DNA strand that is based paired to RNA as transcription proceeds. In this example, the RNA is paired with the bottom strand. The bottom strand is oriented with 3' end to the left and 5' end to the right. The _________ strand (non-template) is complementary and anti-parallel to the _________ strand. Therefore the coding strand is oriented with the 5' end to the left and the 3' end to the right.
The RNA polymerase reads the template strand from the 3' to 5' direction, and synthesizes RNA from 5' to 3'. The template strand is the DNA strand that is based paired to RNA as transcription proceeds. In this example, the RNA is paired with the bottom strand. The bottom strand is oriented with 3' end to the left and 5' end to the right. The coding strand (non-template) is complementary and anti-parallel to the template strand. Therefore the coding strand is oriented with the 5' end to the left and the 3' end to the right.
3' poly-A tail
cleavage of pre-mRNA downstream of polyadenylation sequence by cleavage factors and addition of 20-200 A nucleotides
Transcription by RNA pol II in eukaryotes begins when TFIID recognizes and binds to the ______ box. The bound TFIID helps recruit TFIIA, TFIIB, TFIIF, and RNA pol II. Once those subunits of the minimal initiation complex are bound, TFIIE and TFIIH bind to form the complete initiation complex. Assembly of the complete initiation complex releases RNA pol II, which begins synthesizing the RNA transcript in the 5′ → 3′ direction. After the first 20-30 nucleotides have been synthesized, a cap consisting of a _____________ is added to the 5′ end of the pre-mRNA. ______ removal occurs as RNA pol II continues to elongate the pre-mRNA. When the __________ signal has been transcribed, a ______ tail is added to the 3′ end of the pre-mRNA. Polyadenylation is usually coupled with the termination of transcription.
Transcription by RNA pol II in eukaryotes begins when TFIID recognizes and binds to the TATA box. The bound TFIID helps recruit TFIIA, TFIIB, TFIIF, and RNA pol II. Once those subunits of the minimal initiation complex are bound, TFIIE and TFIIH bind to form the complete initiation complex. Assembly of the complete initiation complex releases RNA pol II, which begins synthesizing the RNA transcript in the 5′ → 3′ direction. After the first 20-30 nucleotides have been synthesized, a cap consisting of a methylated guanine is added to the 5′ end of the pre-mRNA. Intron removal occurs as RNA pol II continues to elongate the pre-mRNA. When the polyadenylation signal has been transcribed, a poly-A tail is added to the 3′ end of the pre-mRNA. Polyadenylation is usually coupled with the termination of transcription.
_____________ is the process by which mRNA shifts by 3 bases in the 5' direction along the ribosome to bring another codon into the A site.
Translocation
Guanine and adenine are purines found in DNA. True or False.
True.
Describe 5' capping.
addition of guanosine monophosphate to 5' end via a 5'-to-5' triphosphate linkage and subsequent methylation of guanine and sometimes additional nucleotides to the pre-mRNA
Describe intron splicing.
removal of intron from pre-mRNA and joining of adjacent exons by spliceosome