As the session is already over but generally there will be no issue if you have a dropped one year as the only thing which matters is your percentage as it should be more than 90 so that you can easily get admission in your desired college of DU.

Good Luck!!!!

There is no any issue with one year gap after 12th you can apply for B.Sc in Delhi University. You should have more than 90% as a general category in class 12th to take admission in your desired field of B.sc. This year the session is already over so you can apply next year.

Good Luck!