GRE Subject Test: Biology : Understanding Structures and Proteins in DNA

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Structures And Proteins In Dna

What is the name of the globular protein around which DNA is wrapped in a chromosome?

Possible Answers:

Chromatin

Nucleolus

Nucleosome

Histone

Correct answer:

Histone

Explanation:

Chromosomes have a great deal of protein involved in their structure so that DNA can be tightly coiled in order to fit into the nucleus. At the smallest level of organization, the DNA wraps itself around small globular proteins called histones. Complexes of histones and DNA form nucleosomes, which appear as "beads" on the DNA strand.

Chromatin refers to the decondensed DNA that has not formed separate chromosomes. The nucleolus is a nuclear structure where ribosomal subunits are synthesized.

Example Question #2 : Understanding Structures And Proteins In Dna

Proteins that DNA wraps around to form tightly packaged and organized structural units are referred to as __________.

Possible Answers:

None of the other answers 

chromosomes

chromatin

nucleosomes

histones

Correct answer:

histones

Explanation:

The correct answer is histones. Histones are alkaline proteins in the nucleus that organize DNA into structural units called nucleosomes. Chromatin and chromosomes are more complex structural units composed of DNA, histones, nucleosomes, and other proteins. 

Example Question #3 : Understanding Structures And Proteins In Dna

Which of the following proteins is necessary for nucleosome formation?

Possible Answers:

Histone methyltransferases

Histones

DNA ligase

Chromatin

Nuclear lamin

Correct answer:

Histones

Explanation:

The correct answer is histones. DNA wraps around histones to form the nucleosomes. Further condensation of many nucleosomes results in chromatin (DNA state). Histone methyltransferases are important enzymes that modify histones during epigenetic gene regulation; however, they are not necessary for nucleosome formation. DNA ligase is responsible for catalyzing the formation of phosphodiester bonds, but is unrelated to nucleosome formation.

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