Mayim Bialik -- Good Genes or Good Docs?

Mayim Bialik's looks are bangin'!

Here's a 13-year-old version of the "Blossom" leading lady back in 1989 (left) and 27 years later the 40-year-old mother of two ... and 'Big Bang Theory' babe ... at a party in Los Angeles earlier this month (right).

Bazinga!

The question is ...