Chapter 12 Flashcards
1) The genetic code is said to be triplet, meaning that there ________.
A) are three amino acids per base in mRNA
B) are three bases in mRNA that code for an amino acid
C) may be three ways in which an amino acid may terminate a chain
D) are three “nonsense” triplets
E) None of the answers listed is correct.
B) are three bases in mRNA that code for an amino acid
2) A class of mutations that results in multiple contiguous (side-by-side) amino acid changes in proteins is probably caused by which one of the following types of mutations? A) frameshift B) transversion C) transition D) base analog E) recombinant
A) frameshift
3) When scientists were attempting to determine the structure of the genetic code, Crick and coworkers found that when three base additions or three base deletions occurred in a single gene, the wild-type phenotype was sometimes restored. These data supported the hypothesis that ________.
A) the code is triplet
B) the code contains internal punctuation
C) AUG is the initiating triplet
D) the code is overlapping
E) there are three amino acids per base
A) the code is triplet
4) Significant in the deciphering of the genetic code was the discovery of the enzyme polynucleotide phosphorylase. What is this enzyme used for?
A) manufacture of synthetic RNA for cell-free systems
B) ribosomal translocation
C) peptide bond formation
D) production of ribosomal proteins
E) degradation of RNA
A) manufacture of synthetic RNA for cell-free systems
5) In 1964, Nirenberg and Leder used the triplet binding assay to determine specific codon assignments. A complex of which of the following components was trapped in the nitrocellulose filter?
A) ribosomes and DNA
B) free tRNAs
C) charged tRNA, RNA triplet, and ribosome
D) uncharged tRNAs and ribosomes
E) sense and antisense strands of DNA
C) charged tRNA, RNA triplet, and ribosome
6) What is the initiator triplet in both prokaryotes and eukaryotes? Which amino acid does this triplet recruit? A) UAA; no amino acid called in B) UAA or UGA; arginine C) AUG; arginine D) AUG; methionine E) UAA; methionine
D) AUG; methionine
7) When examining the genetic code, it is apparent that ________.
A) there can be more than one amino acid for a particular codon
B) AUG is a terminating codon
C) there can be more than one codon for a particular amino acid
D) the code is ambiguous in that the same codon can code for two or more amino acids
E) there are 44 stop codons because there are only 20 amino acids
C) there can be more than one codon for a particular amino acid
8) Introns are known to contain termination codons (UAA, UGA, or UAG), yet these codons do not interrupt the coding of a particular protein. Why?
A) UAA, UGA, and UAG are initiator codons, not termination codons.
B) Exons are spliced out of mRNA before translation.
C) These triplets cause frameshift mutations, but not termination.
D) More than one termination codon is needed to stop translation.
E) Introns are removed from mRNA before translation
E) Introns are removed from mRNA before translation
9) What is the name given to the three bases in a messenger RNA that bind to the anticodon of tRNA to specify an amino acid placement in a protein? A) protein B) anti-anticodon C) cistron D) rho E) codon
E) codon
10) The genetic code is fairly consistent among all organisms. The term often used to describe such consistency in the code is \_\_\_\_\_\_\_\_. A) universal B) exceptional C) trans-specific D) overlapping E) None of the answers listed is correct
A) universal
11) The relationship between a gene and a messenger RNA is that ________.
A) genes are made from mRNAs
B) mRNAs are made from genes
C) mRNAs make proteins, which then code for genes
D) genes are structurally identical to mRNAs
E) mRNA is directly responsible for making Okazaki fragments
B) mRNAs are made from genes
12) When considering the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA polymerase(s) binds. Which of the following is a common consensus sequence? A) TATA B) GGTTC C) TTTTAAAA D) any trinucleotide repeat E) satellite DNAs
A) TATA
13) It has been recently determined that the gene for Duchenne muscular dystrophy (DMD) is more than 2000 kb (kilobases) in length; however, the mRNA produced by this gene is only about 14 kb long. What is a likely cause of this discrepancy?
A) The exons have been spliced out during mRNA processing.
B) The DNA represents a double-stranded structure, whereas the RNA is single-stranded.
C) More amino acids are coded for by the DNA than by the mRNA.
D) The introns have been spliced out during mRNA processing.
E) When the mRNA is produced, it is highly folded and therefore less long.
D) The introns have been spliced out during mRNA processing.
14) An intron is a section of ________.
A) protein that is clipped out posttranslationally
B) RNA that is removed during RNA processing
C) DNA that is removed during DNA processing
D) transfer RNA that binds to the anticodon
E) carbohydrate that serves as a signal for RNA transport
B) RNA that is removed during RNA processing
15) Which of the following two terms relate most closely to split genes? A) 5'-cap, 3'-poly-A tail B) introns, exons C) elongation, termination D) transcription, translation E) heteroduplex, homoduplex
B) introns, exons
16) Which of the following contains the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes?
A) 5’-capping, 3’-poly(A) tail addition, splicing
B) 3’-capping, 5’-poly(A) tail addition, splicing
C) removal of exons, insertion of introns, capping
D) 5’-poly(A) tail addition, insertion of introns, capping
E) heteroduplex formation, base modification, capping
A) 5’-capping, 3’-poly(A) tail addition, splicing
17) If one compares the base sequences of related genes from different species, one is likely to find that corresponding \_\_\_\_\_\_\_\_ are usually conserved, but the sequences of \_\_\_\_\_\_\_\_ are much less well conserved. A) exons; introns B) introns; exons C) introns; chaperons D) chaperons; exons E) introns; proteins
A) exons; introns
18) In which cellular organelle do the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes occur? A) nucleus B) cytoplasm C) mitochondrion D) lysosome E) Golgi
A) nucleus
19) Describe the direction of information flow in living systems. Use appropriate, scientific terms in your description.
DNA is replicated and passed to offspring through reproductive processes. Information contained in DNA is transcribed into a variety of RNAs. Certain RNAs (tRNA) carry amino acids to the site of translation where proteins are assembled. mRNA provide a mechanism for ordering the sequence of amino acids in proteins.
20) Sidney Brenner argued that the code was nonoverlapping because he considered that coding restrictions would occur if it were overlapping. A second major argument against an overlapping code involved the effect of a single nucleotide change. In an overlapping code, how many adjacent amino acids would be affected by a point mutation? In a nonoverlapping code, how many amino acid(s) would be affected?
two; one
