Structure of DNA:
DNA is a thread-like structure composed of nucleotides. These nucleotides are made up of a phosphate group, a sugar molecule, and a nitrogenous base.

Functional part of DNA:
The functional part of DNA is the gene.

Genes:
Genes are segments of DNA that contain the instructions for building proteins. These instructions are in the form of a specific sequence of nucleotides.

Chromatin:
Chromatin is a complex of DNA and proteins that make up chromosomes. It is the material that makes up the chromosomes within the nucleus of eukaryotic cells. Chromatin helps in the organization and packaging of DNA.

Chromosome:
Chromosomes are structures made of condensed chromatin that carry genetic information. They are visible under a microscope during cell division. Chromosomes contain many genes that are responsible for various traits and characteristics.

Conclusion:
In conclusion, DNA is a thread-like structure that contains genes, which are the functional units responsible for carrying genetic information. Chromatin and chromosomes are also important components of DNA, playing roles in DNA organization and cell division.