Which of these statements about nucleosomes are correct?

a. The histones H2A, H2B, H3, and H4 make up the nucleosome octamer that binds DNA.

b. Most histones are small (less than 150 amino acid residues), basic proteins rich in Lys and Arg.

c. DNA binding to histones has the same effect as positive supercoiling.

d. Degradation of linker DNA yields DNA fragments of about 200 bp.

e. Partial enzymatic digestion of chromatin results in DNA fragments of about 103 bp.

Question

Jazlyn Conway

Biology

23 April, 05:13

Which of these statements about nucleosomes are correct?

a. The histones H2A, H2B, H3, and H4 make up the nucleosome octamer that binds DNA.

b. Most histones are small (less than 150 amino acid residues), basic proteins rich in Lys and Arg.

c. DNA binding to histones has the same effect as positive supercoiling.

d. Degradation of linker DNA yields DNA fragments of about 200 bp.

e. Partial enzymatic digestion of chromatin results in DNA fragments of about 103 bp.

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Answers (1)

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Bucko · Answer 1

The correct answers are a. "The histones H2A, H2B, H3, and H4 make up the nucleosome octamer that binds DNA", b. "Most histones are small (less than 150 amino acid residues), basic proteins rich in Lys and Arg". and d. "Degradation of linker DNA yields DNA fragments of about 200 bp".

Explanation:

Nucleosomes are the basic structures that constitute DNA packaging. There are features that characterize nucleosomes, including:

a. "The histones H2A, H2B, H3, and H4 make up the nucleosome octamer that binds DNA". Two each of these four histones make a nucleosome octamer, which binds and wraps approximately 1.7 turns of DNA.

b. "Most histones are small (less than 150 amino acid residues), basic proteins rich in Lys and Arg". Most histones have between 120 to 150 amino acid residues, and have Lys and Arg residues that are target for methylation.

d. "Degradation of linker DNA yields DNA fragments of about 200 bp". Nucleosome along with linker DNA and linker histone form a structural motif that is essential for the formation of chromatin. Each nucleosome binds to approximately 200 bp of DNA, therefore degradation of DNA linker yields of DNA fragments of about this length.