Molecules and Cells Launchpad 3

Alternative splicing means that: A some transcripts are spliced while others are not. B different spliced forms contain different combinations of exons. C some transcripts are spliced correctly and others incorrectly. D alternating introns are removed.

B

Muscle cells make different proteins than nerve cells because they have different sequences of DNA. True False

FALSE

No exceptions to the central dogma exist. RNA is always transcribed from DNA, and RNA is translated to produce proteins. False True

FALSE

Which of the following statements about polycistronic RNA are true and which are false? It is found primarily in eukaryotes. True False

FALSE

Which of the following statements about polycistronic RNA are true and which are false? It has two or more promoters. True False

FALSE

Which of the following statements about polycistronic RNA are true and which are false? Only one protein is produced during translation. True False

FALSE

An exon is: A part of an intact, mature mRNA that leaves the nucleus. B a series of amino acids at the end of a new polypeptide that directs transcription to the ER. C a protein that is clipped out post-translationally. D RNA that is removed during the processing of an RNA molecule and remains inside the nucleus. E a transfer RNA that binds to the codon.

A

The base uracil pairs with: A adenine. B guanine. C cytosine. D thymine.

A

The idea that, when life originated on Earth, a macromolecule other than DNA served the role of information storage and that this same macromolecule carried out catalysis is called the _____ hypothesis. A RNA world B macromolecular world C water world D carbon world

A

Alternative splicing allows for: A different polypeptides to be made from a single gene. B two or more different proteins to be made from a single processed mRNA. C increased stability of a mature mRNA. D enhanced recognition of an mRNA by a ribosome. E multiple genes to be used to code for a single polypeptide chain.

A

A template strand of DNA is read in the _____ direction in order to direct synthesis of RNA in the _____ direction. A 3'-5'; 3'-5' B 3'-5'; 5'-3' C 5'-3'; 5'-3' D 5'-3'; 3'-5'

B

Assuming that transcription and translation both proceed from left to right, which is the correct orientation of the DNA template, the RNA transcript, and the protein product? A DNA template 5'- ......... -3' RNA transcript 3'- ......... -5' Protein product HOOC- ....... ..-NH2 B DNA template 3'- ......... -5' RNA transcript 5'- ......... -3' Protein product H2N- ....... -COOH C DNA template 3'- ......... -5' RNA transcript 5'- ......... -3' Protein product HOOC- ....... ..-NH2 D DNA template 5'- ......... -3' RNA transcript 5'- ......... -3' Protein product H2N- ....... -COOH

B

High levels of transcription of RNA from DNA in eukaryotes usually require: A general transcription factors. B All of these choices are correct. C RNA polymerase. D transcriptional activators (specific transcription factors) E a promoter sequence.

B

How many different types of aminoacyl tRNA synthetases are there? A 64 B 20 C 2 D 4 E 61

B

In a messenger RNA, the cap is needed to: A initiate transcription. B initiate translation. C All of these choices are correct. D initiate replication.

B

In eukaryotes, activator proteins bind to _____; generalize transcription factors bind to _____. A promoters; terminators B enhancers; promoters C promoters; enhancers D DNA polymerases; RNA polymerases E terminators; RNA polymerases

B

If you made a change in the promoter sequence in the DNA that inactivates the promoter, what would happen at the RNA level? A The DNA helicase would not be able to recognize and bind the DNA, so the RNA would not be made. B Nothing, the RNA would be made as usual. C The RNA polymerase would not be able to recognize and bind the DNA, so no RNA would be made. D The mutation of the DNA would be carried through to the RNA sequence.

C

In a messenger RNA, the cap is present at the: A 3' end of the poly(A) sequence. B 5' end of the poly(A) sequence. C 5' end. D 3' end.

C

In messenger RNA, the protein-coding sequence is present in: A introns and the poly(A) sequence. B exons and the poly(A) sequence. C exons. D introns.

C

RNA processing consists of the: A addition of a poly(A) sequence. B addition of a cap. C All of these choices are correct. D removal of introns.

C

The poly(A) sequence that is added to RNA during processing: A is needed for ribosomes to attach to messenger RNA. B aids in the accuracy of translation of the messenger RNA into protein. C helps prevent rapid breakdown of the messenger RNA D helps prevent formation of complex three-dimensional structures in the messenger RNA.

C

Transcription continues until: A a transcription factor signals the end of the gene. B all bases in the DNA are copied. C a terminator sequence is encountered. D a ribosome pulls RNA polymerase off the DNA. E a stop codon is encountered.

C

An mRNA molecule has a sequence 5'- CAGAUCUAAUGCUUAUCGGAU-3'. When translated in a laboratory setting in which translation can be initiated anywhere along the molecule, how many reading frames are possible? A 4 B 6 C 2 D 3 E 1

D

Imagine you are following a particular tRNA, called tRNAQ, through the process of translation in a eukaryote. In what order does tRNAQ go through the steps listed below? (Note that some steps may be used more than once.) 1. The polypeptide is transferred to tRNAQ. 2. tRNAQ binds the A site of the ribosome. 3. tRNAQ binds the P site of the ribosome. 4. The ribosome shifts, with tRNAQ still bound. 5. tRNAQ binds the E site of the ribosome. A 3, 1, 4, 2, 4, 5 B 2, 4, 1, 4, 2, 4, 5 C 3, 4, 1, 4, 2, 4, 5 D 2, 1, 4, 3, 4, 5 E 5, 1, 4, 3, 4, 5

D

The type of RNA that physically interacts with a ribosome, providing the sequence information for a specific protein, is abbreviated: A snRNA. B siRNA. C tRNA. D mRNA. E rRNA

D

Which one of the following is specific to the synthesis of only one type of protein? A a transfer RNA B a ribosome C an aminoacyl tRNA synthetase D a messenger RNA E an elongation factor

D

here does the energy come from to add a uracil to the 3' end of a growing transcript? A the cell's supply of ATP B the hydrolysis of all three phosphate groups from the incoming UTP molecule C the hydrolysis of a terminal phosphate from the incoming UTP molecule D the energy released by allowing the uracil to complementary base pair with an adjacent thymine E the hydrolysis of pyrophosphate from the incoming UTP molecule

E

n eukaryotes, the molecule(s) responsible for promoter recognition is/are referred to as: A the mediator complex. B an enhancer. C the TATA box. D the sigma factor. E general transcription factors.

E

All RNA is translated to generate proteins. True False

FALSE

All introns have identical lengths and sequences. False True

FALSE

During transcription of a given protein-coding gene, both strands are used as template. False True

FALSE

An RNA transcript is synthesized in which direction? A 5' to 3' B N terminus to C terminus C C terminus to N terminus D 3' to 5' E 5' to 5'

A

Transcription starts at a _____ and ends at a _____. A promoter; terminator B 5' cap; terminator C 3' end; 5' end D promoter; 5' end

A

RNA processing occurs in the: A plasma membrane. B cytoplasm. C nucleus and cytoplasm. D nucleus.

D

An intron is: A an RNA sequence that is removed during the processing of an RNA molecule in the nucleus. B a type of transfer RNA. C a polypeptide that is clipped out of a larger protein post-translationally. D part of an intact, mature mRNA that leaves the nucleus. E part of an RNA transcript that is not present in the DNA template.

A

In eukaryotes, newly synthesized proteins encoded in genes in the nucleus are found in the _____ and DNA are observed in the _____. A cytoplasm; nucleus B nucleus; cytoplasm C cytoplasm; cytoplasm also D nucleus; nucleus also or the cytoplasm E nucleus; nucleus also

A

LOOK AT PICTURE ON ANSWER SIDE If the RNA transcript resulting from the DNA sequence above is present in the mRNA and translated codon by codon from one end to the other, which of the following polypeptides would correspond to this part of the mRNA? (Use Table 4.1 to answer this question.) A NH2 - Met-Ile-Gly-Ser-Ile-His -COOH B NH2 - Tyr-Leu-Ala-Arg-Lue-Val -COOH C COOH- Tyr-Leu-Ala-Arg-Lue-Val - NH2 D COOH- Met-Ile-Gly-Ser-Ile-His - NH2

A

Transcription is sometimes described as a process in which RNA is "copied" from the template strand of DNA. This statement is potentially misleading because: A All of these choices are correct. B RNA nucleotides contain ribose and so cannot be an exact copy of DNA. C the RNA transcript and the DNA template strand are antiparallel. D the RNA transcript has a complementary sequence of bases to the template strand. E RNA molecules contain uracil instead of thymine

A

What is the name of the enzyme complex that forms at the start of transcription? A RNA polymerase B DNA polymerase C RNA helicase E DNA gyrase

A

Which of the following is essential, even in an RNA world? A polymerase B transfer RNA C translation D spliceosomes E transcription

A

Which of the following molecules is made during the process of transcription? A All of these choices are correct. B rRNA (ribosomal RNA) C mRNA (messenger RNA) D tRNA (transfer RNA)

A

Which of the following occurs in the P site of the ribosome during translation? A The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon. B None of the other answer options is correct. C An incoming charged tRNA binds to this site. D An uncharged tRNA is ejected from this site as the ribosome slides to the next codon.

A

Which of the following types of post-transcriptional modification is common in eukaryotes? A All of these choices are correct. B intron removal C polyadenylation and intron removal D polyadenylation E 5' cap addition

A

Which one of the following explains why rRNAs are the most abundant type of RNA in a mammalian cell? A There are rRNAs in ribosomes, and it takes millions of ribosomes to translate all the proteins required for a cell's functions. B A different type of ribosome is needed to synthesize all of a cell's proteins, and because most proteins are present in multiple copies, a huge number of ribosomes are needed. C It takes several rRNAs to transcribe a single mRNA, so there are many more rRNAs needed in a cell than the number of proteins synthesized. D None of the other answer options is correct. rRNAs are not the most abundant type of RNA in a mammalian cell. E There are more different types of rRNA genes than all other types of genes combined.

A

LOOK AT PICTURE ON ANSWER SIDE What will happen when the ribosome shifts one codon further on the mRNA, assuming the next codon is NOT a stop codon? (Select all that apply.) A The tRNA that was carrying the polypeptide will be ejected from the ribosome. B The tRNA carrying the polypeptide will be in the P site. C The sites of the ribosomes will be relabeled (from left to right) P, A, E. D A new tRNA will bind to the ribosome. E The tRNA that is shown in the A site in the figure above will be ejected from the ribosome.

A, B, D

A template DNA strand contains 30% A, 20%T, 27% G, and 23% C. The RNA transcript contains: A 30% T, 20% A, 27% C, and 23% G. B 30% U, 20% A, 27% C, and 23% G. C 30% A, 20% T, 27% G, and 23% C. D 30% A, 20% U, 27% G, and 23% C.

B

In an RNA world: A RNA functions for information storage and there is no catalysis. B RNA functions for information storage and for catalysis. C None of the other answer options is correct. D RNA functions for information storage and proteins do catalysis. E DNA functions for information storage and RNA does catalysis.

B

In eukaryotes, the AUG codon that starts translation is: A at the 5' end of the mRNA. B the AUG nearest the 5' cap on the mRNA. C None of the other answer options is correct. D adjacent to the 5' cap on the mRNA. E adjacent to a Shine-Dalgarno sequence.

B

In the process of transcription, the RNA transcript is synthesized: A from the 3' end to the 5' end. B from the 5' end to the 3' end.

B

In transcription, each added ribonucleotide comes into the RNA polymerase complex as a: A nucleoside diphosphate. B nucleoside triphosphate. C nucleoside monophosphate. D nucleoside (= a nucleotide with no phosphate)

B

In transcription, the energy to attach each successive ribonucleotide to the growing RNA chain comes from: A cleavage of the 2' hydroxyl group on the ribose of the incoming nucleotide. B cleavage of the high-energy phosphate bonds of the incoming nucleotide. C cleavage of the high-energy phosphate bonds in the growing transcript. D the RNA polymerase itself.

B

In which of the following ribosomal sites does the anticodon of a tRNA pair completely with the mRNA codon? A none of the sites B the A site and the P site C the P site only D the P site and the E site E the A site only

B

Many promoters of a hypothetical conserved gene have mostly adenines and thymines. What is the MOST likely reason for this high proportion of adenines and thymines? A None of the other answer options is correct. B This is the region for separating template and nontemplate strands, and A-T base pairs are easier to separate than G-C base pairs. C It is possible to create more unique sequences for recognition with adenines and thymines than it is with guanines and cytosines. D Accessory proteins like sigma factors or transcription factors bind more easily to AT-rich sequences than they do to GC-rich sequences. E RNA polymerases are better at incorporating uracils and thymines into RNA molecules than incorporating guanines and cytosines.

B

Translation is the process by which: A ribosomes read the information in a DNA molecule and use it to synthesize protein. B ribosomes synthesize protein from information in an RNA molecule. C an RNA molecule is used to repair damage to a related DNA molecule. D the information in DNA is used to synthesize an exact copy of that DNA. E a section of DNA is used as information to generate an RNA molecule.

B

When a peptide bond is created between two amino acids: A the carboxyl group of the first amino acid is joined to the carboxyl group of the second. B the carboxyl group of the first amino acid is joined to the amino group of the second. C the amino group of the first amino acid is joined to the amino group of the second. D the amino group of the first amino acid is joined to the carboxyl group of the second.

B

Which of the following brings amino acids to the ribosome for use in translation? A rRNA (ribosomal RNA) B tRNA (transfer RNA) C mRNA (messenger RNA)

B

Which of the following cellular processes occurs in the nucleus of a eukaryote? A transcription B transcription and RNA processing C All of these choices are correct. D RNA processing E translation

B

Which of the following occurs in the A site of the ribosome during translation? A An uncharged tRNA is ejected from this site as the ribosome slides to the next codon. B An incoming charged tRNA binds to this site. C The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon. D None of the other answer options is correct.

B

polycistronic mRNA with six protein-coding genes has: A 6 start codons and 1 stop codon. B 6 start codons and 6 stop codons. C 3 start codons and 3 stop codons. D 1 start codon and 6 stop codons. E 1 start codon and 1 stop codon.

B

Which steps facilitate the initiation of eukaryotic transcription ? (Select all that apply.) A Sigma factor binds to the promoter. B General transcription factors bind to the promoter. C DNA looping brings transcriptional activator proteins, general transcription factors, mediator complex and RNA Pol II together. D DNA looping brings transcriptional activator proteins, general transcription factors, sigma factor and RNA Pol II together. E Transcriptional activator proteins bind to enhancers.

B, C, E

After translation has been initiated, for how long does elongation go on? A until the cell runs out of tRNAs B until the ribosome reaches an AUG codon C until the ribosome reaches a UAA, UAG, or UGA codon D until the ribosome reaches the end of the mRNA E until the ribosome reaches the poly(A) tail of the mRNA

C

Imagine that you and your colleagues are working in a lab to develop a protein synthesis system for a new type of synthetic cell. During your brainstorming sessions, you propose that polycistronic mRNA would be much more useful than mRNA that is only translated into one protein. This would allow for multiple proteins necessary for a particular function to be translated together. One of your colleagues says that is a good idea, but if you decide to go with polycistronic mRNA, you'd better make sure to use a prokaryotic translation system. Why might it be problematic to use a eukaryotic translation system with polycistronic mRNA? A Eukaryotic start and stop codons are different from prokaryotic start and stop codons. B Prokaryotic ribosomes do not detach from mRNA when they reach a stop codon. C Eukaryotic ribosomes initiate translation by binding to the 5′-cap, which is only at the end of the mRNA. D Introns would always prevent translation of the mRNA.

C

In eukaryotes, general transcription initiation factors bind A 5' cap B terminator C RNA polymerase D transcriptional activators

C

Which one of the following types of RNAs carries information for making a single type of protein? A ribosomal RNA B transfer RNA C messenger RNA D small interfering RNA E small nuclear RNA

C

Referring to the following mRNA sequence, 5'AUGAGACUUACCGAA3', what would the anti-codon look like if the second nucleotide of the fourth codon was mutated to "U"? A 3′AAC5′ B 3′AUG5′ C 3′TAG5′ D 3′UAG5′

D

Ribosomes in prokaryotes and eukaryotes are: A identical in structure but translate using different genetic codes. B similar in structure and translate using different genetic codes. C identical in structure and translate using the same genetic code. D similar in structure and translate using the same genetic code.

D

The genetic code is: A comprised of codons which usually differ at the first position. B a quadruplet code. C ambiguous. D redundant. E different for bacteria than for eukaryotes.

D

ibose differs from deoxyribose in that a ribose: A is missing a hydroxyl group. B has an extra phosphate group. C is missing a phosphate group. D has an extra hydroxyl group.

D

n prokaryotes, newly synthesized proteins are found in the _____ and DNA are observed in the _____. A cytoplasm; nucleus B nucleus; cytoplasm C nucleus; nucleus also and the cytoplasm D cytoplasm; cytoplasm also E nucleus; nucleus also

D

In an RNA world: A RNA functions in information storage and proteins do catalysis. B RNA functions in information storage and there is no catalysis. C DNA functions in information storage and RNA alone catalyzes reactions. D None of the other answer options is correct. E RNA functions in information storage and for catalysis.

E

In what order does a charged tRNA move through the sites of a ribosome? A The tRNA binds with the E site, then is moved to the P site, then the A site as the ribosome shifts. B The tRNA binds with the P site, then is moved to the A site, then the E site as the ribosome shifts. C The tRNA binds with the E site, then is moved to the A site, then the P site as the ribosome shifts. D The tRNA binds with the A site, then is moved to the E site, then the P site as the ribosome shifts. E The tRNA binds with the A site, then is moved to the P site, then the E site as the ribosome shifts. F The tRNA binds with the P site, then is moved to the E site, then the A site as the ribosome shifts.

E

RNA splicing is a component of: A None of the other answer options is correct. B RNA translation. C RNA transcription. D RNA replication. E RNA processing.

E

An exon is considered a "coding sequence" of DNA, and its information is retained in the processed mRNA within a cell. True False

TRUE

In a long double-stranded DNA molecule containing the genetic information for many genes, the template strand for one gene may be the nontemplate strand for another gene along the way. False True

TRUE

The sequence of amino acids in a protein is referred to as its primary structure. False True

TRUE

Which of the following statements about polycistronic RNA are true and which are false? Translation of the mRNA may begin before transcription is finished. True False

TRUE

Whichever DNA strand is transcribed, the RNA polymerase reads the template strand from 3′ to 5′. True False

TRUE