If you, or any source you are reading are claiming that DNA can survive the process that forms a diamond, it is hard to take that seriously.

The most hardy protein such as DNA cannot survive temperatures much more than 100 degrees C. and a couple of atmospheres of pressure.

For diamonds form naturally...

"The formation of natural diamond requires very specific conditions—exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars (4.5 and 6 GPa), but at a comparatively low temperature range between approximately 900 and 1,300 °C (1,652 and 2,372 °F). These conditions are met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.[10]"