AP BIO: 16 – Flashcards
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In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that ______.
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The genetic material of the phage is DNA
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Up until Hershey and Chase showed that DNA was the genetic molecule, what molecule was considered the best candidate for carrying genetic information and why?
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Proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed.
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What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?
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X-ray crystallography
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The two sugar-phosphate strands of a DNA molecule are joined to each other through _____.
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hydrogen bonds between nucleotide bases
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A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced int he host cell would have ____.
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the protein and DNA of T4
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Who is credited with explaining the structure of the DNA double helix?
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Watson and Crick
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Why were many of the early experiments on DNA carried out on viruses and bacteria?
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They have short generation times, relatively small genomes, their chromosomes have a simpler structure, and can interact with each other
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During Griffith's experiments with Streptococcus Pneumoniae in mice, material from _____ bacteria transformed _____ bacteria.
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heat-killed virulent; living nonvirulent
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The rate of elongation in prokaryotes is _____ the rate in eukaryotes.
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much faster than (500 nucleotides per second in bacteria and 50 in human cells)
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The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by _____.
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DNA polymerase I. Upon encountering the RNA primer, DNA polymerase II falls off the DNA and is replaced by DNA polymerase I.
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Which of the following attributes of DNA is most crucial to its accurate duplication?
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Its specific base pairing and hydrogen bonding
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During the replication of DNA, _____.
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both strands of a molecule act as templates
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The role of DNA polymerases in DNA replication is to _____.
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attach free nucleotides to the new strand.
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Unlike prokaryotic DNA replication, replication of eukaryotic chromosomes _____.
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cannot be completed by DNA polymerase. This is because eukaryotic chromosomes are linear and DNA polymerase cannot replicate the extreme 3' end of the template strands
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Chargaff found that for DNA _____.
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The ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
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Which description of DNA replication is correct?
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Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates
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After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand?
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helicases, primase, DNA polymerase, ligase. First the double helix is unwound; primase makes the RNA primer; DNA polymerase elongates the growing strand and replaces the RNA primer with DNA; and DNA ligase joins the Okazaki fragments
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Put the following containing entities in order according to the amount of DNA found in their genomes.
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virus, bacteria, eukaryote.
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The information in DNA is contained in _____.
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the sequence of nucleotides along the length of the two strands of the DNA molecule.
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DNA polymerase adds nucleotides to the _____ of the leading strands, and to the _____ of the lagging strands (Okazaki fragments)
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3' end; 3' end. Although leading and lagging strands are synthesized in opposite directions with respect to movement of the replication fork, DNA polymerase enzyme can only add nucleotides to the 3' end of a growing DNA strand.
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What is the major difference between bacterial chromosomes and eukaryotic chromosomes?
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Bacteria have a single circular chromosome while eukaryotes have several linear choromsomes
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Which of the following components is (are) required for DNA replication?
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RNA primer
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What enzyme joins Okazaki fragments?
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DNA ligase. Helicases unwind the DNA; polymerase synthesizes the complementary strands; ligase joins the Okazaki fragments
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In DNA, the two purines are _____, and the two pyrimidines are _____.
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adenine and guanine; cytosine and thymine. Purines have two rings, and pyrimidines have one.
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Which of the following is correct?
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Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine.
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Telomeres _____.
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get shorter with continued cell division.
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One strand of a DNA molecule has the base sequence 5'-ATAGGT-3'. The complementary base sequence on the other strand of DNA will be 3'-_____-5'.
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TATCCA
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The incorporation of an incorrect base into the DNA during replication _____.
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can be repaired by the mismatch repair system
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At each end of a DNA replication bubble is _____.
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a replication fork
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The overall error rate in the completed DNA molecule is approximately _____.
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1 error per 10,000,000,000 nucleotides
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Monomers for the synthesis of DNA are called _____.
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nucleotides
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Which set of enzymes is involved in nucleotide excision repair?
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nuclease, DNA polymerase, and ligase
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In what way(s) is our traditional representation of DNA polymerase molecules moving like locomotives along a track inaccurate?
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The proteins involved in replication do not move; instead, DNA is drawn through the complex and like a train on a track, DNA polymerase must add nucleotides sequentially. It cannot jump around
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The two strands of a DNA double helix are antiparallel. This means that _____.
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one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction
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The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called _____.
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Topoisomerase. It cuts the DNA and allows it to spin around its central axis and relieves the strain caused by twisting.
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The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that _____.
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Both have a sugar-phosphate backbone. All DNA occurs as a double helix with two sugar phosphate backbones that are antiparallel to each other.
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The experiments of Meselson and Stahl showed that DNA
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replicated in a semiconservative fashion
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Telomerase _____.
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is an enzyme that lengthens telomeres.
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Individuals with the disorder xeroderma pigmentosum _____.
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are hypersensitive to sunlight, have high rates of skin cancer, often have inherited defects in the nucleotide excision repair system, and have difficulty repairing thymine dimers.
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The "beads on a string" seen in interphase chromatin are _____.
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nucleosomes. They are complexes of DNA wrapped around 8 histone molecs.
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Which of the following statements about replication origins is correct?
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Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins, the two strands of DNA at teh origin are separated, allowing the formation of a replication bubble, in bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin, in both prokaryotes and eukaryotes, replication proceeds in both directions from each origin.
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Avery and his colleagues' 1944 experiment showed that DNA _____.
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was the substance that transformed the bacteria in Griffith's experiment
