All GRE Subject Test: Biology Resources
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?
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 __________.
None of the other answers
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?
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.