Here’s a 75mb joke:

There were 2 sperm, swimming along.

One says to the other one:

“We’ve been swimming for ages. How long until the egg yet?”

The other replies:

“The egg!? Oh. It’s not for miles yet. We’ve only just passed the tonsils.”

Edit:

This calculation is off by an order of magnitude.

The human genome has about 3.1 billion base pairs. Each sperm has half of that. Ignoring epigenetics, each base pair has four options (A/T/C/G), so it can be represented by two bits each.

All told, that’s 3.1 gigabits = 388 megabytes per gamete.

Oh, in that case then, I guess that’s a 776mb joke.