All GRE Subject Test: Biology Resources
Example Questions
Example Question #1 : Chromatin And Chromosomes
What is the name of the globular protein around which DNA is wrapped in a chromosome?
Histone
Nucleolus
Chromatin
Nucleosome
Histone
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 : Chromatin And Chromosomes
Proteins that DNA wraps around to form tightly packaged and organized structural units are referred to as __________.
chromatin
histones
chromosomes
nucleosomes
None of the other answers
histones
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 #1 : Understanding Structures And Proteins In Dna
Which of the following proteins is necessary for nucleosome formation?
Histones
Histone methyltransferases
Nuclear lamin
Chromatin
DNA ligase
Histones
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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