Answer
Each chromosome is a double stranded helical molecule of DNA. Nuclear DNA is stored in the nucleus, but the nucleus is a small organelle, and storage space is at a premium. In preparation for efficient storage in the nucleus, each DNA molecule is wrapped around an octet of histone isomers-- in the manner of a thread wrapped around a spool. In this case, the "thread" is the core DNA and the "spool" is the histone octect. This structure thus formed is called a nucleosome. Linking nucleosomes are lengths of intervening DNA , the so-called "linker DNA".There is further secondary and tertiary folding of chromaffin strands partly to make the most economical use of scare nuclear space as well as to protect DNA, and facilitate gene expression.
Work Step by Step
Some of the details of this folding pattern of DNA or chromaffin threads in the nucleus are not visible by light microscopy. But ultrastructural examination of this reveals a very complex and not completely understood pattern.
