AP Biology Unit 6

What kind of chemical bond is found between paired bases of the DNA double helix?

• hydrogen

• ionic

• covalent

What is meant by the description ʺantiparallelʺ regarding the strands that make up DNA?

• The 5ʹ to 3ʹ direction of one strand runs counter to the 5ʹ to 3ʹ direction of the other strand.

• One strand is positively charged and the other is negatively charged.

Which enzyme catalyzes the elongation of a DNA strand in the 5ʹ → 3ʹ direction?

• primase

• DNA ligase

• DNA Polymerase

• helicase

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

• the nucleotide sequence of the template strand

• the primase used in the reaction

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent

• leading strands and Okazaki fragments

• lagging strands and Okazaki fragments.

Which of the following separates the DNA strands during replication?

• helicase

• DNA polymerase

• primase

A new DNA strand elongates only in the 5ʹ to 3ʹ direction because

• DNA polymerase can only add nucleotides to the free 3ʹ end

• Okazaki fragments prevent elongation in the 3ʹ to 5ʹ direction.

When DNA is compacted by histones into 10 nm and 30 nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

• methylation and phosphorylation of histone tails

• nucleotide excision and reconstruction

Based your answer on the figure: A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?

• an accumulation of A and no production of B and C

• an accumulation of A and B and no production of C

Tags

NGSS.HS-LS3-2

In which of the following actions does RNA polymerase differ from DNA polymerase?

• RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.

• RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to double-stranded DNA.