Hi Farose Neiyas Hussain,
Thank you for posting in the Microsoft Community Forum.
If you are trying to add the attribute "Gender" to all objects within a particular OU, you can architecturally extend AD. After the extension you can specify that the attribute "Gender" exists for all objects within an OU or any other attribute you want to add.
But AD architecture extension is not a simple thing, here is an official MS article about AD architecture extension, you can follow the teaching in the article to extend the architecture of your own environment:Publishing and the Active Directory schema - Configuration Manager | Microsoft Learn
Best regards
Neuvi Jiang