It is commonly proposed to look for life based on silicon, based on it's relative abundance and similarity to carbon. However, carbon and silicon are not completely interchangeable. The bond strength between carbon or silicon and itself is different, thus, some molecules with high chain length can not be replicated with silicone. Similarely, molecules such as proteins, for which all carbon atoms are replaced with silicon, would not retain their form and thus not their function.
Is life based on silicone still possible, just under a different environment?
This would affect how we should look for aliens. Also, if silicon based life is unlikely, is there some other element that could lead to life?