5: How many base sequences?

Ready for some big numbers?

Our story so far: George claims to have found a new, unique sequence of DNA which codes for the
sleuthing gene. It is 165 nucleotides long.

Bess has pooh-poohed her friend’s claim, stating that all possible 165 nucleotide sequences have
already been discovered.

In fact, about how many unique 165-nucleotide sequences are possible?

A googol is “one” with a hundred zeros, right? So the answer to the problem above (“2” with 99 zeros) is a bit more than one-fifth of a googol. It is a seriously huge number. If it doesn’t boggle your mind, you need to get your mind-boggler checked.

one google written out

Put another way, there are a fifth of a google of distinct nucleotide sequences that would code for a 55-amino-acid peptide. That’s an awful lot of sequences. And it seems pretty unlikely that they’ve all been discovered already!