7. DNA and Chromosome Structure

Histone proteins are responsible for what?

Which of the following is the correct order of chromosomal packaging levels?

What is the name of the enzyme that removes supercoils in DNA?

Give descriptions for the following terms:

Chromosome territory

Give descriptions for the following terms:

Nucleosome

Give descriptions for the following terms:

Heterochromatin

Give descriptions for the following terms:

Euchromatin

Give descriptions for the following terms:

G bands

Give descriptions for the following terms:

Scaffold proteins

Give descriptions for the following terms:

Nucleosome core particle

In the discussion, we focused on how DNA is organized at the chromosomal level. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:

How did we learn that eukaryotic chromatin exists in the form of repeating nucleosomes, each consisting of about 200 base pairs and an octamer of histones?

The human genome contains 2.9×10⁹ base pairs. Approximately how many nucleosomes are required to organize the 10-nm–fiber structure of the human genome? Show the calculation you use to determine the answer.

In eukaryotic DNA, how does the role of H1 differ from the role of H3 in chromatin formation?

In eukaryotic DNA, along a 6000-bp segment of DNA, approximately how many molecules of each kind of histone protein do you expect to find? Explain your answer.

In eukaryotic DNA, where are you most likely to find histone protein H1?