DNA Structure And Replication Practice Questions Flashcards
In Griffith’s experiment, why did the heat-killed virulent bacteria combined with live non-virulent bacteria
cause disease in mice?
A) The live non-virulent bacteria acquired the ability to replicate independently.
B) The heat-killed bacteria reactivated and caused disease.
C) A “transforming principle” from the heat-killed virulent bacteria entered the live non-virulent
bacteria, making them virulent.
D) The immune response of the mice was suppressed by the heat-killed bacteria.
C) A “transforming principle” from the heat-killed virulent bacteria entered the live non-virulent
bacteria, making them virulent.
In Avery’s experiments, what was the significance of selectively degrading DNA, RNA, and proteins in the
bacterial extracts?
A) To prove that protein and RNA do not influence bacterial virulence.
B) To determine which molecule carried the “transforming principle” by observing whether
transformation still occurred after each molecule was destroyed.
C) To isolate bacterial enzymes that promote transformation.
D) To determine the relative abundance of macromolecules in bacterial cells.
B) To determine which molecule carried the “transforming principle” by observing whether
transformation still occurred after each molecule was destroyed.
What critical evidence did Hershey and Chase provide to confirm DNA as the hereditary material in
bacteriophages?
A) They observed that labeled DNA, but not labeled protein, entered bacterial cells and was passed
on to new phages.
B) They showed that both protein and DNA are required for viral replication.
C) They demonstrated that RNA could act as a genetic material in viruses.
D) They proved that proteins in bacteriophages are essential for infecting bacteria
A) They observed that labeled DNA, but not labeled protein, entered bacterial cells and was passed
on to new phages.
Why was the use of isotopes (³²P and ³⁵S) crucial in the Hershey-Chase experiment?
A) They allowed the researchers to distinguish between DNA and protein based on their incorporation
into different parts of the bacteriophage.
B) They selectively destroyed DNA and protein to observe the transformation process.
C) They labeled the viral RNA to determine its role in infection.
D) They identified the chemical structure of nucleotides.
A) They allowed the researchers to distinguish between DNA and protein based on their incorporation
into different parts of the bacteriophage.
In the Meselson and Stahl experiment, what result provided direct evidence for semiconservative DNA
replication?
A) The appearance of only “light” DNA after the first generation of replication.
B) The appearance of an intermediate-density (“hybrid”) band after the first generation and both
hybrid and “light” DNA after the second generation.
C) The continuous presence of only “heavy” DNA throughout all generations.
D) The formation of entirely new double helices after the first generation.
B) The appearance of an intermediate-density (“hybrid”) band after the first generation and both
hybrid and “light” DNA after the second generation.
What is the primary structure of DNA?
A) A single strand of amino acids
B) A polymer of nucleotides
C) A double-stranded protein
D) A lipid bilayer
B) A polymer of nucleotides
Which nitrogenous bases pair together in DNA?
A) A pairs with G, T pairs with C
B) A pairs with C, G pairs with T
C) A pairs with T, G pairs with C
D) A pairs with U, G pairs with T
C) A pairs with T, G pairs with C
What type of bond connects the sugar-phosphate backbone in DNA?
A) Hydrogen bond
B) Phosphodiester bond
C) Ionic bond
D) Peptide bond
B) Phosphodiester bond
What did Chargaff discover about DNA?
A) The base ratios are variable across species.
B) The amount of A equals that of T, and the amount of G equals that of C.
C) The double helix structure of DNA.
D) DNA is the transforming principle.
B) The amount of A equals that of T, and the amount of G equals that of C.
What is the mode of DNA replication?
A) Conservative
B) Semiconservative
C) Dispersive
D) Parallel
B) Semiconservative
What is the function of helicase in DNA replication?
A) Unwinding the DNA double helix
B) Synthesizing RNA primers
C) Adding nucleotides to the growing strand
D) Sealing gaps between DNA fragments
A) Unwinding the DNA double helix
What are the short DNA fragments formed on the lagging strand called?
A) Leading strand fragments
B) Watson fragments
C) Telomeric fragments
D) Okazaki fragments
D) Okazaki fragments
Which enzyme removes RNA primers during replication?
A) DNA polymerase III
B) DNA polymerase I
C) Ligase
D) Topoisomerase
B) DNA polymerase I
In DNA replication, new nucleotides are added to which end of the strand?
A) 5’
B) 3’
C) Both ends simultaneously
D) Neither; nucleotides are inserted randomly
B) 3’
What is the main function of telomeres?
A) They replicate the leading strand.
B) They protect the ends of chromosomes from degradation.
C) They prevent the double helix from unwinding.
D) They synthesize RNA primers.
B) They protect the ends of chromosomes from degradation.
