Lambda phage consists of a virus particle including a head (also known as a capsid), a tail, and tail fibers

Lambda DNA fragments prepared by the digestion of purified lambda DNA with the restriction endonuclease Hind III. On agarose gel electrophoresis the mixture separates into eight individual bands having the following number of base pairs: 23130, 9416, 6557, 4361, 2322, 2027, 564, and 125.

The head contains the phage's double-stranded circular DNA genome. The phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial cell. Lambda phage DNA is commonly used as a DNA molecular weight marker.