Heat-killed bacteria harbor the constituent(s) necessary to convey genetic properties to living bacteria.
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To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _____.
answer
Incubated nonvirulent cells with the complete extract.
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If Avery had observed transformation using only the extracts containing degraded DNA, degraded RNA, and degraded protein, but NOT the extract containing degraded polysaccharides, he would have concluded that ____.
answer
Polysaccharides are the genetic material.
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The Hershey and Chase experiments involved the preparation of two different types of radioactively labeled phage. Which of the following best explains why two preparations were required?
answer
It was necessary that each of the two phage components, DNA and protein, be identifiable upon recovery at the end of the experiment.
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What best represents the central conclusion of the Hershey-Chase experiments?
answer
DNA is the identity of the hereditary material in phage T2.
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What outcome would be most likely if the Hershey-Chase experiments were repeated without the step involving the blender?
answer
Both preparations of infected bacteria would exhibit radioactivity.
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What conclusions did Griffith draw from his experiments?
answer
A transforming factor from a virulent strain of bacteria can make non-virulent strain virulent.
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True/False. Guanine and adenine are purines found in DNA.
answer
True.
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What is a true statement about DNA?
answer
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions.
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What is the complementary DNA sequence to 5' ATGCTTGACTG 3' ?
answer
5' CAGTCAAGCAT 3'
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Dna is composed of 4 different types of ___. Each one is made up of a pentose ___, a ____ group, and one of 4 _____.
answer
nucleotides, sugar, phosphate, nitrogenous bases.
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Adenine, guanine, cytosine, and thymine are _____.
answer
nitrogenous bases.
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Adenine and guanine, which have nine-member double-ring, are called ___.
answer
purines
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Cytosine and thymine, which have a six-member single-ring, are called ____.
answer
pyrimidines.
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Deoxyribonucleotides bind together to form polynucleotides. This bond occurs between the phosphate group of one nucleotide and the C ___' position of a ____ of another nucleotide. The type of bond formed in this interaction is called a _____ bond.
answer
3, sugar, phosphodiester.
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The nitrogenous bases of each nucleotide project ____ the double helix. Therefrom complementary base pairs through the formation of _____ bonds with bases on the opposite DNA strand.
answer
into, hydrogen.
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Adenine complementarily binds with thymine and forms ___ ___ bonds.
answer
2 hydrogen.
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Guanine complementarily binds with cytosine and forms ____ ____ bonds.
answer
3 hydrogen.
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Statements about the basic structural feature of DNA.
answer
In a DNA macromolecule, the two strands are complementary and antiparallel. The twisting of the DNA double helix is attributed to the tight packing of DNA bases and base-stacking.
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The results of the Meselson-Stahl experiments relied on all of the following except____.
answer
The fact that DNA is the genetic material
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After observing the results of one round of replication, the scientists obtained results from a second round. The purpose of one additional round of replication was to ____.
answer
distinguish betweenness-conservative and dispersive replication.
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What would results from a third round of replication using the methods of Meselson and Stahl?
answer
One light band and one intermediate band.
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Helicase function?
answer
Binds at the replication fork and breaks H-bonds between bases.
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Topoisomerase function?
answer
Binds ahead of the replication fork and breaks covalent bonds in DNA backbone.
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Single-strand binding protein function?
answer
Prevents H-bonds between bases and binds after the replication fork.
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What makes up the protein component of a nucleosome?
answer
Two tetramers of histone proteins.
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What is the first order of chromatin packing?
answer
Coiling around nucleosomes.
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True/False. The second order of chromatin packing occurs when nucleosomes coil together to form a fiber that is 300 nm in diameter.
answer
True.
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What determines which DNA strand is the template strand, and therefore in which direction RNA polymerase II moves along the DNA?
answer
The specific sequence of bases along the DNA strands.
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What describes the process that takes place before a mature mRNA exits the nucleus?
answer
noncoding sequences called introns are placed by molecular complexes called spliceosomes. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
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Which region of a tRNA molecule binds to amino acids?
answer
3' codon.
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What best describes the function of ammoniacal tRNA synthetase?
answer
It attaches a specific amino acid to a tRNA molecule.
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True/False. Each aminoacyl tRNA syntheses is specific for one amino acid and a small number of tRNAs.
answer
True.
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The Beadle and Tatum experiments were based on all of the following assumptions except that ____.
answer
Two strains of auxotrophic Neurospora that grow on minimal medium supplemented with biotin have mutations in the same gene.
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In the first round of screening, Beadle and Tatum plated spores on minimal medium. The purpose of this screen was to ____.
answer
Determine whether any auxotrophic mutants had been generated.
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What can be inferred from the Beadle ad Tatum experiments?
answer
For a mutation resulting in the production of a defective enzyme involved in a biosynthetic pathway, the compound preceding the corresponding step will accumulate.
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True/False. Tautomers of nucleotide bases are isomers that differ from each other in the location of one hydrogen atom in the molecule.
answer
True.
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Which nucleotide will base-pair with the enol form of 5-bromouracil?
answer
Guanine.
question
When event could result in a frameshift mutation?
answer
base deletion
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What are the consequences of having pyrimidine dimers in DNA?
answer
These dimers distort the DNA structure and result in errors during DNA replication.
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True/False. Thymine dimers can be repaired by Photoreactive Repair or Nucleotide Excision Repair.
answer
True.
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True statement regarding Nucleotide Excision Repair (NER) and Base Excision Repair (BER).
answer
Both NER and BER involved the removal of one or more damaged bases by a nuclease.
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True/False. All compounds that have been found to be mutagenic in the Ames test are also carcinogenic.
answer
False. The Ames test is used as a preliminary screening tool. Not all compounds that give a positive Ames test are carcinogenic.
question
Why are liver extracts used in the Ames test?
answer
Liver enzymes may activate some innocuous compounds, making them mutagenic.
question
Which bacteria grow on the agar plate if the Ames test is positive?
answer
his+ prototrophs.
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