주다 in 말해 주다 is an auxiliary verb. 말해 주다 means "to tell for, let someone know" 말해 줘 is a casual way of saying 말해 준다/줍니다(declarative present) 내 혈관 속 DNA가 말해 줘 The DNA in my blood vessel let me know. There are many auxiliary verb in Korean. -버리다 completion e.g. 읽어 버리다 to finish reading 먹어 버리다 to finish eating -내다 willful action e.g. 받아 내다 to end up collecting 먹어 밀어내다 to push off and drive out -나다 spontaneous e.g. 일어 나다 to get up 살아 나다 to come alive -주다 benefactive (for someone) e.g. 봐 주다 to watch for 사 주다 to buy for -드리다 benefactive (for someone)(HONORIFIC) e.g. 도와 드리다 to help someone -보다 experience e.g. 입어 보다 to try on (clothes) 써 보다 to try writing -대다 repetition e.g. 웃어 대다 to keep laughing 졸라 대다 to keep begging -두다 accumulation e.g. 써 두다 to write and keep 모아 두다 to gather and keep -넣다 placing into e.g. 접어 넣다 to fold and put away 사 넣다 to buy and put away -놓다 placing/keeping e.g. 넣어 놓다 to place into/put away 사 놓다 to buy and keep -가지다 possession e.g. 집어 가지다 to pick up and keep 사 가지다 to buy and keep -지다 change of state automatically / by itself e.g. 커지다 to grow big 젊어지다 to get younger 써지다 to be written 열려지다 to open by itself -가다(1) "take" e.g. 가져 가다 to take (away from speaker) 사 가다 to buy and take -가다(2) to progress (from now on) e.g. 다해 가다 to be almost done 끝나 가다 to be about to finish -오다(1) "bring" e.g. 가져 오다 to bring (to speaker) 잡아 오다 to catch and bring 싸 오다 to wrap and bring -오다(2) have been ... (since past) e.g. 먹어 오다 to have been eaten 일해 오다 to have been worked -있다 "in the state of" (sitting, placed) e.g. 앉아 있다 is sitting (position) 놓여 있다 is placed Above expressions are common in speech and writing Below expressions are common in speech -빠지다 emphasize on quality of "extremely", "very". It works with an adjective e.g. 착해 빠지다. too nice 흔해 빠지다. too common 늙어 빠지다. too old -쌓다 ‘repeat excessively’ e.g. 울어 쌓다. is crying non-stop 먹어 쌓다. do keep eating

내 혈관 속 DNA가 말해줘 = DNA in my blood tell me something. 줘 original from is 주다's one of meaning is giving permission, therefore, 말해줘 means something let me know something.