Organisms and Populations — BIOLOGY STD 12 Science — Question

$I$. In the absence of adenosine deaminase enzyme, purine metabolism is disturbed and $T-$lymphocytes fails to function $II$. $ADA$ deficiency is caused by the deletion of the gene for $ADA$

$III$. In some cases, it can be cured by bone marrow transplantation and enzyme replacement therapy. But in both approaches, the patients are not completely cured

$IV$. For permanent cure, genes isolated from the bone marrow cells producing $ADA$ at early embryonic stages can be a possible cure

Which of the above statements are correct?