In an episode of the BBC program QI – Quite Interesting, the great Stephen Fry comes to ask: How much information do you think is in the DNA of a small sperm …?
And he answers: they are 37.5 MB. In a normal male ejaculation, it is equivalent to 15,875 GB. That is approximately 7,500 information laptops. However, Are your figures correct? Maybe it fell short.
The Twitter account summarizes Fry’s claims as follows:
A sperm has 37.5 MB of DNA info. One ejaculation transfers 15,875 GB of data, equivalent to that held on 7,500 laptops.
– Quite Interesting (@qikipedia) July 14, 2012
But maybe the numbers should be higher if we calculate what Wikipedia says.
The haploid human genome (23 chromosomes) is approximately 3 billion base pairs long and contains around 30,000 genes. Since each base pair can be encoded by 2 bits, we have about 750 megabytes of data.
A single somatic (diploid) cell contains twice this amount, that is, about 6 billion base pairs.
Men have less than women because the Y chromosome is approximately 57 million base pairs, while the X is approximately 156 million, but in terms of information, men have more because the second X contains almost the same information as the first. Since individual genomes vary in sequence by less than 1% from each other, variations of a given human genome from a common reference can be compressed losslessly to approximately 4 megabytes.
Genome entropy rate differs significantly between coding and non-coding sequences. It is close to the maximum of 2 bits per base pair for coding sequences (approximately 45 million base pairs), but less for non-coding parts. It varies between 1.5 and 1.9 bits per base pair for the individual chromosome, except for the Y chromosome, which has an entropy rate of less than 0.9 bits per base pair.
Thus, it’s actually over 30,000 TB of DNA encoded information if your sperm count is not low. This means that the egg resists this DDoS attack at 1.5 terabytes per second, and only lets one data packet through, making it the best firewall in the world! The downside is that this one small data packet that you let go crashes your system for 9 months.