*Transcription and Translation

If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides? 1 2 3 4 12

2

An extraterrestrial life form is discovered. It has a genetic code much like that of organisms on Earth except that there are five different DNA bases instead of four and the base sequences are translated as doublets instead of triplets. How many different amino acids could be accommodated by this genetic code? 5 10 25 64 32

25

The following question refers to Figure 17.1 (see word Document). A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be 5' TTG-CTA-CAG-TAG 3'. 3' AAC-GAC-GUC-AUA 5'. 5' AUG-CTG-CAG-TAT 3'. 3' AAA-AAT-ATA-ACA 5'. 3' AAA-GAA-TAA-CAA 5'.

3' AAA-GAA-TAA-CAA 5'.

A particular triplet of bases in the template strand of DNA is 5 - AGT - 3 . The corresponding codon for the mRNA transcribed is 5 - AGT - 3 5 - UGA - 3 5 - TCA - 3 . 5 - ACU - 3 either UCA or TCA, depending on wobble in the first base

5 - ACU - 3

The following question refers to Figure 17.1 (see word Document). A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA codes for this peptide? 3' UUU-CCC-AAA-GGG-UUU-CCC 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG 5' TTT-CCC-AAA-GGG-TTT-CCC 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA

5' TTT-CCC-AAA-GGG-TTT-CCC

A particular eukaryotic protein is 300 amino acids long. Which of the following could be the maximum number of nucleotides in the DNA that codes for the amino acids in this protein? 3 300 900 903 1,800

903

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that some tRNAs have anticodons that recognize two or more different codons. the rules for base pairing between the third base of a codon and tRNA are flexible. many codons are never used, so the tRNAs that recognize them are dispensable. A and B only A, B, and C

A and B only

During translation, chain elongation continues until what happens? No further amino acids are needed by the cell. All tRNAs are empty. The polypeptide is long enough. A stop codon is encountered. The ribosomes run off the end of mRN

A stop codon is encountered.

Which of the following does not occur during the termination phase of translation? A termination codon causes the A site to accept a release factor. The newly formed polypeptide is released. A tRNA with the next amino acid enters the P site. The two ribosomal subunits separate. Translation stops.

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

The function of the ribosome in polypeptide synthesis is to hold mRNA and tRNAs together. catalyze the addition of amino acids from tRNAs to the growing polypeptide chain. move along the mRNA and eject tRNAs during the translocation process. A and B only A, B, and C

A, B, and C

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 synthetase

Translation occurs in the cytoplasm. a lysosome. the nucleus. a mitochondrion. a nucleoplasm.

the cytoplasm.

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

Both A and C are correct.

All of the following are directly involved in translation except mRNA tRNA ribosomes. DNA aminoacyl-tRNA synthetase enzymes.

DNA

What is the effect of a nonsense mutation in a gene? It changes an amino acid in the encoded protein. It has no effect on the amino acid sequence of the encoded protein. It introduces a stop codon into the mRNA It alters the reading frame of the mRNA It prevents introns from being expressed.

It introduces a stop codon into the mRNA

Which of the following are transcribed from DNA? protein exons rRNA B and C only A, B, and C

NOT A, B, and C OR rRNA OR exons

A particular triplet of bases in the coding strand of DNA is AAA The anticodon on the tRNA that binds the mRNA codon is TTT. UUU. AAA either UAA or TAA, depending on first base wobble.

UUU

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

a base deletion near the start of a gene

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? a base-pair deletion a codon substitution a substitution in the last base of a codon a codon deletion a point mutation

a base-pair deletion

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

base pairing of activated methionine-tRNA to AUG of the messenger RNA

Accuracy in the translation of mRNA into the primary structure of a protein depends on specificity in the binding of ribosomes to mRNA shape of the A and P sites of ribosomes. bonding of the anticodon to the codon. attachment of amino acids to tRNAs. both C and D

both C and D

What are ribosomes composed of? rRNA only proteins only both rRNA and protein mRNA, rRNA, and protein mRNA, tRNA, rRNA, and protein

both rRNA and protein

The anticodon of a particular tRNA molecule is complementary to the corresponding mRNA codon. complementary to the corresponding triplet in rRN the part of tRNA that bonds to a specific amino acid. changeable, depending on the amino acid that attaches to the tRNA catalytic, making the tRNA a ribozyme.

complementary to the corresponding mRNA codon.

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

either an insertion or a deletion of a base.

What are the coding segments of a stretch of eukaryotic DNA called? introns exons codons replicons transposons

exons

What are polyribosomes? groups of ribosomes reading a single mRNA simultaneously ribosomes containing more than two subunits multiple copies of ribosomes associated with giant chromosomes aggregations of vesicles containing ribosomal RNA ribosomes associated with more than one tRNA

groups of ribosomes reading a single mRNA simultaneously

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

hydrogen bonding between base pairs

All of the following are found in prokaryotic mRNA except the AUG codon. the UGA codon. introns. uracil. cytosine.

introns.

Which of the following is not directly involved in the process of translation? ligase tRNA rRNA mRNA aminoacyl-tRNA synthetase

ligase

A codon consists of two nucleotides. may code for the same amino acid as another codon. consists of discrete amino acid regions. catalyzes RNA synthesis. is found in all eukaryotes, but not in prokaryotes.

may code for the same amino acid as another codon.

The following question refers to Figure 17.1 (see word Document). What amino acid sequence will be generated, based on the following mRNA codon sequence? 5'AUG-UCU-UCG-UUA-UCC-UUG 3' met-arg-glu-arg-glu-arg met-glu-arg-arg-gln-leu met-ser-leu-ser-leu-ser met-ser-ser-leu-ser-leu met-leu-phe-arg-glu-glu

met-ser-ser-leu-ser-leu

Which of the following represents a similarity between RNA and DNA? Both are double-stranded. the presence of uracil the presence of an OH group on the 2' carbon of the sugar nucleotides consisting of a phosphate, sugar, and nitrogenous base Both are found exclusively in the nucleus.

nucleotides consisting of a phosphate, sugar, and nitrogenous base

The following question refers to Figure 17.1 (see word Document). What is the sequence of a peptide based on the mRNA sequence 5'- UUUUCUUAUUGUCUU-3' ? leu-cys-tyr-ser-phe cyc-phe-tyr-cys-leu phe-leu-ile-met-val leu-pro-asp-lys-gly phe-ser-tyr-cys-leu

phe-ser-tyr-cys-leu

Of the following types of mutations, which one is likely to be the most common? point mutation base-pair substitution nonsense mutation frameshift mutation missense mutation

point mutation

Which of the following helps to stabilize mRNA by inhibiting its degradation? TATA box spliceosomes 5' cap poly-A tail None of the above

poly-A-tails

What is the most abundant type of RNA? mRNA tRNA rRNA pre-mRNA hnRNA

rRNA

Which of the following is not a part of the eukaryotic transcription initiation complex? promoter RNA polymerase transcription factors snRNP TATA box

snRNP

When does translation begin in prokaryotic cells? soon after a transcription elongation begins as soon as the RNA polymerase binds the promoter once the pre-mRNA has been converted to mRNA as soon as the DNA introns are removed from the template

soon after a transcription elongation begins

QUESTION 21 What is an anticodon part of? DNA tRNA mRNA a ribosome an activating enzyme

tRNA

Base-pair substitutions involving the third base of a codon are unlikely to result in an error in the polypeptide. This is because substitutions are corrected before transcription begins. substitutions are restricted to introns. the base-pairing rules are less strict for the third base of codons and anticodons. a signal-recognition particle corrects coding errors. transcribed errors attract snRNPs, which then stimulate splicing and correction.

the base-pairing rules are less strict for the third base of codons and anticodons.

Introns are significant to biological evolution because their presence allows exons to be moved around more easily, creating proteins with new combinations of functional domains. they protect the mRNA from degeneration. they are translated into essential amino acids. they maintain the genetic code by preventing incorrect DNA base pairings. they correct enzymatic alterations of DNA bases.

their presence allows exons to be moved around more easily, creating proteins with new combinations of functional domains

Which of the following is least related to the other items? translation TATA box transcription template strand RNA polymerase

translation