DNA Replication Quiz (Unit 6 Standard B)

Which of the following is NOT true of DNA replication?

• Helicase unwinds the DNA strands.

• DNA polymerase requires RNA primers to initiate DNA synthesis.

• DNA is synthesized in the 3’ to 5’ direction.

• Ligase joins the fragments on the lagging strand.

Which of the following statements best explains the mechanism for DNA replication?

• DNA replication is reductive, because half the total DNA present is copied.

• DNA replication is semi-conservative, because each DNA strand serves as a template during replication.

• DNA replication is dispersive, because the two resulting DNA molecules are mixtures of parent and daughter DNA.

• DNA replication is conservative, because one resulting molecule is identical to the original and the other consists of two new strands.

In DNA replication, DNA "unwinds" to form two template strands: the leading strand and the lagging strand.  Which of the following statements about these strands is true?

• Okazaki fragments are used to synthesize the leading strand of DNA.

• DNA polymerase can only synthesize DNA on the leading strand.

• The lagging strand can only be synthesized once the leading strand has been completed.

• The leading strand of DNA is synthesized continuously.

A model of a process involving nucleic acids is shown in Figure 1.  Which of the following best explains what process is represented in Figure 1 ?

• New DNA strands are being synthesized in the 3′ to 5′ direction from their DNA templates.

• New DNA strands are being synthesized in the 5′ to 3′ direction from their DNA templates.

• A new RNA strand is being synthesized in the 3′ to 5′ end from its DNA template.

• Two new RNA strands are being synthesized in both directions from their DNA templates.

Figure 1 shows some relevant details of a model of how a deoxynucleotide, in this case dTMP, is added to a growing strand of DNA. The features of this model provide evidence for which explanation of why all growing strands are synthesized in a 

5′ to 3′ direction?

• The two strands need to be antiparallel to bond properly. 

• Thymine and adenine would not bond properly if the strand grew from 3′ to 5′. 

• The translation of mRNA occurs in the 5′ to 3′ direction; therefore, the growing DNA strand must also grow in the 5′ to 3′ direction.

• The phosphate group, attached to the 5′ carbon of the dTMP, forms a covalent bond with the oxygen atom attached to the 3′ carbon of the growing strand.

Figure 1 illustrates a model of the molecules involved in DNA replication and their placement relative to each other. Which of the following correctly explains where DNA replication will begin on the strand oriented 5′→3′, reading from left to right?

• DNA replication will be randomly initiated along the unwound portion of the DNA strand since base pairing will occur.

• DNA replication cannot occur since there is already RNA base pairing with the template strand.

• DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.

• DNA replication will be initiated at the site of the topoisomerase since that is where DNA begins to uncoil.