Show your students how DNA is organized in the nucleus
of the cell with our 3-D model of the nucleosome, the most basic,
repeating structural unit of chromosomes.
The nucleosome is composed of 145 base pairs of double-stranded DNA
wrapped around a central core of 8 histones – 2 each of: H2A, H2B, H3,
and H4. The N-terminus of each histone has many positively-charged amino
acids that interact with the negatively-charged phosphate groups of the
This 3-D structure reveals that histones interact only with the minor
groove of DNA. The major groove is then available for sequence-specific
DNA binding proteins, such as Zif 268. (See Zinc Finger Mini Model.) It
can be used to demonstrate how DNA is arranged and packaged in the
nucleus, and initiate discussions about how the DNA is accessed by
transcription factors and other regulatory elements. Each histone is
shown in spacefill format and in a different color: H2A is yellow, H2B
is red, H3 is blue, and H4 is green. The DNA backbone is shown in white.
The DNA base pairs are displayed as white hydrogen bonds.
The 1910 Nobel Prize in Physiology or Medicine was awarded to Albrecht Kossel "in
recognition of the contributions to our knowledge of cell chemistry
made through his work on proteins, including the nucleic substances". (In 1896 he discovered histidine, then worked out the classical method for the quantitaive separation of the hexone bases.)
The 1982 Nobel Prize in Chemistry was awarded to Aaron Klug "for
his development of crystallographic electron microscopy and his
structural elucidation of biologically important nucleic acid-protein
This 4'' model is made of plaster by rapid prototyping and should be
handled with care. Mini models will break if dropped, held tightly or
handled roughly. Its PDB file is 1A0I.pdb.