AP Bio Biotechnology

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

Which of the following covalently connects segments of DNA?

• helicase

• DNA polymerase

• ligase

Which of the following synthesizes short segments of RNA?

• helicase

• DNA polymerase

• primase

The leading and the lagging strands differ in that

• the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

• the leading strand is synthesized by adding nucleotides to the 3ʹ end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5ʹ end.

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

The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except

• a gene from an organism could theoretically be expressed by any other organism.

• all organisms have a common ancestor.

• DNA was the first genetic material.

• the same codons in different organisms usually translate into the same amino acids.

Tags

NGSS.HS-LS4-1

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.