Student or Learner
Analysis of the genomes of humans, chimpanzees and macaques indicates that a DNA sequence thought to play a role in the production of these spines have been deleted in humans, but has been preserved in other primates.
Could you explain me the part ...have been deleted in humans? a DNA sequence is singular, after the comma "has been" used its ok but why "has been" not used at first? I don't see any plural object.
So, should have been "has been" right?