1. Which of the following statements about nuclear transport is true?
a. mRNAs and proteins transit the nucleus through different types of nuclear pores.
b. "Nuclear import receptors bind to proteins in the cytosol and bring the proteins to the nuclear pores, where the proteins are released from the nucleus."
c. "Nuclear pores have water-filled pass through in a nonselective fashion."
d. Nuclear pores are made up of many copies of a single protein.

2. Which of the following statements is true?
a. "DNA molecules, like proteins, consist of a single, long polymeric chain that is assembles from small monomeric subunits."
b. The polarity of a DNA strand results from the polarity of the nucleotide subunits.
c. There are five different nucleotides that become incorporated into a DNA strand.
d. Hydrogen bonds between each nucleotide hold individual DNA strands together.

3. What is the role of the nuclear localization sequence in a nuclear protein?
a. It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
b. It aids in protein unfolding so that the protein can thread through nuclear pores.
c. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes.
d. It prevents the protein from diffusing out of the nucleus through nuclear pores.

4. How do changes in histone modifications lead to changes in chromatin structure?
a. They directly lead to changes in the positions of the core histones.
b. They change the affinity between the histone octamer and the DNA.
c. They help recruit other proteins to the chromatin.
d. They cause the histone N-terminal trails to become hyperextended.