Bio 150- Chapter 17

A sequence of pictures of polypeptide synthesis shows a ribosome holding two transfer RNAs. One tRNA has a polypeptide chain attached to it; the other tRNA has a single amino acid attached to it. What does the next picture show? A. The polypeptide chain moves over and bonds to the single amino acid. B. The tRNA with the amino acid leaves the ribosome. C. The amino acid moves over and bonds to the polypeptide chain. D. The tRNA with the polypeptide chain leaves the ribosome. E. A third tRNA with an amino acid joins the pair on the ribosome.

A. The polypeptide chain moves over and bonds to the single amino acid.

Which of the following DNA mutations is the most potentially damaging to the protein it specifies? A. a base-pair deletion B. a codon substitution C. a substitution in the last base of a codon D. a codon deletion E. a point mutation

A. a base-pair deletion

A mutagen is A. a gene that has been altered by a mutation. C. an organism that has been changed by a mutation. D. the portion of a chromosome altered by a mutation. E. any change in the nucleotide sequence of DNA

A. a gene that has been altered by a mutation.

Which of the following are arranged in the correct order by size, from largest to smallest? A. chromosome-gene-codon-nucleotide B. nucleotide-chromosome-gene-codon C. codon-chromosome-gene-nucleotide D. gene-chromosome-codon-nucleotide E. chromosome-gene-nucleotide-codon

A. chromosome-gene-codon-nucleotide

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes A. excision of introns. B. fusion into circular forms known as plasmids. C. linkage to histone molecules. D. union with ribosomes. E. fusion with other newly transcribed mRNA.

A. excision of introns.

Beadle and Tatum showed that each kind of mutant bread mold lacked a specific enzyme. This experiment demonstrated that A. genes carry information for making proteins. B. mutations are changes in genetic information. C. genes are made of DNA. D. enzymes are required to repair damaged DNA information. E. cells need specific enzymes in order to function.

A. genes carry information for making proteins.

What are polysomes? A. groups of ribosomes reading the same mRNA simultaneously B. ribosomes containing more than two subunits C. multiple copies of ribosomes found associated with giant chromosomes D. aggregations of vesicles containing ribosomal RNA E. ribosomes associated with more than one TRNA

A. groups of ribosomes reading the same mRNA simultaneously

Which of the following is NOT directly involved in the process of translation? A. ligase B. tRNA C. rRNA D. mRNA E. aminoacyl-tRNA synthetase

A. ligase

Sickle-cell disease is probably the result of which kind of mutation? A. point mutation only B. frameshift only C. nonsense only D. nondisjunction only E. Both B and D

A. point mutation only

Which of the following is LEAST related to the other items? A. translation B. TATA box C. transcription D. template strand E. RNA polymerase

A. translation

What is the relationship among DNA, a gene, and a chromosome? A. A chromosome contains hundreds of genes, which are composed of protein. B. A chromosome contains hundreds of genes, which are composed of DNA. C. A gene contains hundreds of chromosomes, which are composed of protein. D. A gene is composed of DNA, but there is no relationship to a chromosome. E. A gene contains hundreds of chromosomes, which are composed of DNA.

B. A chromosome contains hundreds of genes, which are composed of DNA.

Which of the following is FALSE? A. Transcriptionally produced gene products are molecules of RNA. B. Eukaryotic proteins are translated in the nucleus. C. Each eukaryotic gene is regulated individually. D. Histones are found only in eukaryotic chromosomes. E. RNA polymerase attaches to DNA at the promoter sequence.

B. Eukaryotic proteins are translated in the nucleus.

Which enzyme synthesize tRNA molecules? A. RNA replicase B. RNA polymerase C. aminoacyl-tRNA synthetase D. ribosome E. ribozymes

B. RNA polymerase

Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein? A. a base substitution B. a base deletion near the start of the coding sequence C. a base deletion near the end of the coding sequence, but not in the terminator codon D. deletion of three bases near the start of the coding sequence, but not in the initiator codon E. a base insertion near the end of the coding sequence, but not in the terminator codon

B. a base deletion near the start of the coding sequence

Before messenger RNA is mature A. all exons are removed B. a cap and tail are added to the transcript C. anticodon are assembled D. the transfer RNA transfers the messenger RNA to the ribosome E. the single RNA strand duplicates itself in much the same way as DNA.

B. a cap and tail are added to the transcript

From the following list, which is the first event in translation in eukaryotes? A. elongation of the polypeptide B. base pairing of activated methionine-tRNA to AUG of the messenger C. binding of the larger ribosomal subunit to smaller ribosome subunits D. covalent bonding between the first two amino acids E. Both B and D occur simultaneously.

B. base pairing of activated methionine-tRNA to AUG of the messenger

Which of the following events in translation of eukaryotes (starting with methionine) occurs first? A. joining of the ribosomal subunits. B. base pairing of met-tRNA to AUG of the messenger RNA. C. binding of the large ribosomal subunit to AUG of MRNA. D. covalent bonding between the first two amino acids. E. forming of polysomes.

B. base pairing of met-tRNA to AUG of the messenger RNA.

What are the coding segments of a stretch of eukaryotic DNA called? A. introns B. exons C. codons D. replicons E. transposons

B. exons

A particular ____ carry the information for making a particular polypeptide, but ____ can be used to make any polypeptide. A. gene and ribosome . . . a tRNA and an mRNA B. gene and mRNA . . . a ribosome and a tRNA C. ribosome and mRNA . . . a gene and a tRNA D. gene and tRNA . . . a ribosome and an mRNA E. tRNA and ribosome . . . a gene and an mRNA

B. gene and mRNA . . . a ribosome and a tRNA

When a ribosome first attaches to an mRNA molecule, one tRNA binds to the ribosome. The tRNA that recognizes the initiation codon binds to the A. amino acid site (A site) of the ribosome. B. peptide site (P site) of the ribosome. C. second tRNA before attaching to the ribosome. D. both A and C are correct.

B. peptide site (P site) of the ribosome.

Which of the following is NOT related to ribosomal activity? A. A site B. spliceosome C. codon recognition D. peptide bond formation E. P site

B. spliceosome

Where is an anticodon present? A. DNA B. tRNA C. mRNA D. ribosome E. activating enzyme

B. tRNA

A gene is A. the same thing as a chromosome. B. the information for making a polypeptide. C. made of RNA. D. made by a ribosome. E. made of protein.

B. the information for making a polypeptide

Which of the following processes occurs in the cytoplasm of a eukaryotic cell? A. DNA replication B. translation C. transcription D. DNA replication and translation E. translation and transcription

B. translation

Choose the answer that has these events of protein synthesis in the proper sequence. 1. An aminoacyl-tRNA binds to the A site. 2. A peptide bond forms, the peptide chain transfers to tRNA on A site 3. tRNA on the E site leaves the ribosome. 4. ribosomal subunits advance one codon on mRNA. 5. the tRNA on A site translocates to the P site, holding the peptide chain. A. 1, 3, 2, 4, 5 B. 4, 1, 2, 5, 3 C. 5, 4, 3, 2, 1 D. 1, 2, 4, 5, 3

D. 1, 2, 4, 5, 3

A particular eukaryotic protein is 300 amino acids long. Which of the following could be the number of nucleotides in the DNA that codes for this protein? A.3 B.100 C.300 D.900 E.1800

D. 900

RNA differs from DNA in that RNA A. contains ribose as its sugar. B. is found only in cytoplasm. C. contains uracil instead of thymine. D. Both A and C are correct. E. A, B, and C are correct.

D. Both A and C are correct.

During translation, chain elongation continues until what happens? A. No further amino acids are needed by the cell. B. All tRNAs are empty. C. The polypeptide is long enough. D. Chain terminator codons enter into A site. E. The ribosomes run off the end of mRNA.

D. Chain terminator codons enter into A site.

All of the following are directly involved in translation EXCEPT A. mRNA. B. tRNA. C. ribosomes. D. DNA. E. aminoacyl tRNA synth

D. DNA.

A polysome is a. one of the units of ribosome B. the nuclear organelle that synthesize RNA C. the two subunits of ribosomes attached together D. an mRNA molecule with several ribosome attached.

D. an mRNA molecule with several ribosome attached.

After an mRNA molecule is transcribed from a eukaryotic gene, portions called ____ are removed and the remaining ____ are spliced together to produce an mRNA molecule with a continuous coding sequence. A. operators . . . promoters B. exons . . . introns C. silencers . . . enhancers D. introns . . . exons E. promoters . . . operators

D. introns . . . exons

In prokaryotes, the primary transcript of structural genes is A. hnRNA. B. tRNA. C. rRNA. D. mRNA. E. DNA.

D. mRNA.

During the process of translation (polypeptide synthesis), ____ matches an mRNA codon with the proper amino acid. A. a ribosome B. DNA polymerase C. ATP D. transfer RNA E. messenger RNA

D. transfer RNA

As a ribosome move along an mRNA molecule by one codon, which of the following occurs? A. The tRNA that was in the A site moves into the P site. B. The tRNA that was in the P site moves into the A site. C. The tRNA that was in the P site moves to E site and departs from the ribosome. D. The tRNA that was in the A site departs from the ribosome. E. Both A and C are correct.

E. Both A and C are correct.

Accuracy in the translation of mRNA into the primary structure of a protein depends on specificity in the A. binding of ribosomes to mRNA. B. shape of the A and P sites of ribosomes. C. bonding of the anticodons to their respective codons. D. attachment of amino acids to their respective tRNAs. E. Both C and D are correct.

E. Both C and D are correct.

A frameshift mutation could result from A. a base insertion only. B. a base deletion only. C. a base substitution only. D. deletion of three consecutive bases. E. either an insertion or a deletion of a base.

E. either an insertion or a deletion of a base.

The flow of information in a cell proceeds A. from RNA to DNA to protein. B. from protein to RNA to DNA. C. from DNA to protein to RNA. D. from RNA to protein to DNA. E. from DNA to RNA to protein.

E. from DNA to RNA to protein.

Which of the following helps to stabilize mRNA by inhibiting its degradation? A. TATA box B. spliceosomes C. introns D. snRNPs E. poly(A) tail

E. poly(A) tail

A geneticist found that a particular mutation had no effect on the polypeptide coded by a gene. This mutation probably involved A. deletion of one nucleotide. B. alteration of the start codon. C. insertion of one nucleotide. D. deletion of the entire gene. E. substitution of one nucleotide.

E. substitution of one nucleotide.

Which of the following does NOT occur during the termination phase of translation? A. A termination codon moves into the A site. B. The newly formed polypeptide is released. C. A tRNA with the next amino acid enters the P site. D. The two ribosomal subunits separate. E. Translation stops.

C. A tRNA with the next amino acid enters the P site.

How does RNA polymerase know where to start transcribing a gene into mRNA? A. It starts at one end of the chromosome. B. Transfer RNA acts to translate the message to RNA polymerase. C. It starts at a certain nucleotide sequence called a promoter. D. The ribosome directs it to the correct portion of the DNA molecule. E. It looks for the AUG start codon.

C. It starts at a certain nucleotide sequence called a promoter

Which of the following is TRUE for both prokaryotic and eukaryotic gene expression? A. After transcription, a 3' poly (A) tail and a 5' cap are added to mRNA. B. Translation of mRNA can begin before transcription is complete. C. RNA polymerase may recognize a promoter region upstream from the gene. D. mRNA is synthesized in the 3' to 5'direction. E. The mRNA transcript is the exact complement of the gene from which it was copied.

C. RNA polymerase may recognize a promoter region upstream from the gene.

5. When RNA is being made, the RNA base ____ always pairs with the base _____ in DNA. A. U . . . T B. T . . . G C. U . . . A D. A . . . U E. T . . . A

C. U . . . A

At one point as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred A. in a double-stranded DNA molecule. B. during translation. C. during transcription. D. when an mRNA codon paired with a tRNA anticodon. E. It is impossible to say, given this information.

C. during transcription.

What type of bonding is responsible for maintaining the shape of the tRNA molecule? A. covalent bonding between sulfur atoms B. ionic bonding between phosphates C. hydrogen bonding between base pairs D. van der Waals interactions between hydrogen atoms E. peptide bonding between amino acids

C. hydrogen bonding between base pairs

Where is the attachment site for RNA polymerase? A. structural gene region B. initiation region C. promoter region D. operator region E. regulator region

C. promoter region

The information carried by a DNA molecule is in A. its amino acid sequence. B. the sugars and phosphates forming its backbone. C. the order of the nucleotides in the molecule. D. the total number of nucleotides it contains. E. the RNA units that make up the molecule.

C. the order of the nucleotides in the molecule.

What are ribosomes composed of? A. two subunits, each consisting of rRNA only B. two subunits, each consisting of several proteins only C. two subunits, each consisting of rRNA and many proteins. D. mRNA, rRNA, and protein E. mRNA, tRNA, rRNA, and protein

C. two subunits, each consisting of rRNA and many proteins.