Across:
   1,12,6dn. Change jumper? To me, no issues in great undertaking to dive into organic fabric (5 6 7)
   4. Graduates, gets amazing praise... these are rungs on life's most important ladder! (4 5)
   9. Dare let out being family? (7)
  10. Bit of sputum gathered as DNA may be extracted (7)
  11. Live in cut back units to convey gain (8)
  12. see 1 across
  14. Friend pursuing origin of Transylvanian count (5)
  15. Luxury is finding effortless introduction for essay (8)
  18. Most clearly defined DNA splicing technique has others losing rights (8)
  20. see 21 down
  22. Employs terrific burst of aphrodisiac (6)
  24. Substitution which makes a scanner a sterner receptacle (8)
  26. Laboratory equipment capturing right waveform (7)
  27. Instructions for life: take this type of acid! (7)
  28. Said how he felt about paying alimony? (9)
  29. Important games which occur in laboratories (5)
Down:
   1. You fathered it... you provide inheritance! (8)
   2. Cryptic clue in bizarre moral scale of mechanisms by which inheritance operates (9)
   3. With fame, if not with skill (7)
   4. Sect behold disintegrating linen where progenitor may have left DNA evidence? (10)
   5. Commando hospital's decoration (4)
   6. see 1 across
   7. Small house with one good toilet (5)
   8. Saturated solution of 21 dioxide establishes 27 origins (6)
  13. Did study again, taking a second to be moderate (10)
  16. Haemal evidence perhaps of small and large plates (9)
  17. Samples taken along with additional CT scans initially (8)
  19. Dot keeps active around cold and lonely base (7)
  20. Loss of fur in sick Thai cur (7)
  21,20ac. Intertwining of two forms essential part of our reproduction (6 5)
  23. Leak about opening of "Hello Dolly" perhaps (5)
  25. 17 from earth, that one 17 from forest? (4)