AP Biology Unit 6 Gene Expression and Gene Regulation

Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism.

Approximately what percentage of the nucleotides in this sample will be thymine?

• 12%

• 24%

• 31%

• 38%

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

• hydrogen

• ionic

• covalent

In an analysis of the nucleotide composition of DNA, which of the following will be found?

• A = G and C = T

• A + C = G + T

Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?

• Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

• Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.

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

Which of the following covalently connects segments of DNA?

• helicase

• DNA polymerase

• ligase