How is the DNA code itself a homology?

Explanation:

These fundamental similarities are most easily explained by evolutionary theory: life shares a common ancestor. ... In fact, the DNA code itself is a homology that links all life on Earth to a common ancestor. DNA and RNA possess a simple four-base code that provides the recipe for all living things.

the DNA code itself is a homology that links all life on Earth to a common ancestor. DNA and RNA possess a simple four-base code that provides the recipe for all living things.

this transfer is call conjunction