You can find DNA in almost every cell of a living organism. However, for DNA extraction, certain tissues are preferred because they contain higher concentrations of DNA or are easier to work with:

Commonly used sources:

* Blood: White blood cells contain a good amount of DNA.

* Saliva: Contains buccal cells that are easily collected.

* Hair follicles: The root of the hair contains cells with DNA.

* Cheek cells: Easily collected by cheek swab.

* Muscle tissue: A good source of DNA, but more invasive to collect.

* Plant tissue: Leaves, roots, and seeds are common sources.

Less common sources:

* Bone: Contains DNA but can be challenging to extract.

* Teeth: Can be used for ancient DNA analysis.

* Other tissues: Almost any tissue can be used for DNA extraction, depending on the specific application.

The specific tissue chosen for DNA extraction depends on the purpose of the analysis and the availability of the sample.