The most common and most likely answer to this crossword clue is the 10 letter word NUCLEOTIDE
I've seen this crossword clue in The Guardian
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More clues leading to the result NUCLEOTIDE
Buddy explains!
The straight part
We know that "it’s in my DNA" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s in my dna = nucleotide.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does NUCLEOTIDE mean?
NUCLEOTIDE noun- The monomer constituting DNA or RNA biopolymer molecules. Each nucleotide consists of a nitrogenous heterocyclic base (or nucleobase), which can be either a double-ringed purine or a single-ringed pyrimidine; a five-carbon pentose sugar (deoxyribose in DNA or ribose in RNA); and a phosphate group.