Bio. Chapt. 17 Quiz – Flashcards
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The nitrogenous base adenine is found in all members of which group?
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ATP, RNA, and DNA.
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Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because
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RNA acts as an expendable copy of the genetic material.
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A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is
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3' UCA 5'.
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What nucleotide triplet best represents a codon?
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A triplet in the same reading frame as an upstream AUG.
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RNA polymerase moves in which direction along the DNA?
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3'→5' along the template strand.
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In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?
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RNA polymerase II.
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Transcription in eukaryotes requires what in addition to RNA polymerase?
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Several transcription factors (TFs).
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What help/s to stabilize mRNA by inhibiting its degradation?
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5' cap and poly (A) tail.
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What are the coding segments of a stretch of eukaryotic RNA called?
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Exons.
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A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 500 amino acids. This is best explained by the fact that
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Many noncoding stretches of nucleotides are present in mRNA.
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Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes
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Excision of introns.
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A mutation in what part of a gene is likely to be most damaging to a cell?
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Exon.
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What is true of snRNPs?
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They join together to form a large structure called the spliceosome.
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Alternative RNA splicing
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Can allow the production of proteins of different sizes from a single mRNA.
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In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic clel after he has removed its 5' cap and poly (A) tail. What would you expect for him to find?
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The molecule is digested by exonucleases since it is no longer protected at the 5' end.
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A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is
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UUU.
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What type of bonding is responsible for maintaining the shape of the tRNA molecule?
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Hydrogen bonding between base pairs.
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What is the most abundant type of RNA?
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rRNA.
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As a ribosome translocates along an mRNA molecule by one codon, what occurs?
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The tRNA that was in the A site moves into the P site.
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The process of translation, whether in prokaryotes or eukaryotes, tequires tRNAs, amino acids, ribosomal subunits, and what?
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Polypeptide factors plus GTP.
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What type of mutation, rsulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
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A deletion of 2 nucleotides.
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What is an example of a frameshift mutation for the sentence THECATATETHERAT?
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THECATARETHERAT.
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A frameshift mutation could result from
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Either an insertion or a deletion of a base.
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What DNA mutation is most likely to be damaging to the protein it specifies?
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A base-pair deletion.
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What point mutation would be most likely to have a catastrophic effect on the functioning of a protein?
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A base deletion near the start of a gene.
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What is the most current description of a gene?
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A DNA sequence that is expressed to form a functional product: either RNA or polypeptide.
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In eukaryotic cells, transcription can't begin until
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Several transcription factors have bound to the promoter.
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The anticodon of a particular tRNA molecule is
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Complementary to the corresponding mRNA codon.
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What is not true of RNA processing?
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Exons are cut out before mRNA leaves the nucleus.
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What component is not directly involved in translation?
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DNA.
