Have Been/Has Been

[Volcano1985]

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.

[bhaisahab]

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.

I'd imagine that it's an error.

[Volcano1985]

So, should have been "has been" right?

[bhaisahab]

So, should have been "has been" right?

Yes, I would say so.

[Volcano1985]

Thanks, Sir.