Summary: Guy is lactose intolerant. He inserts a sequence providing lactose tolerance into an adeno-associated virus. He then infects himself with this virus, which inserts the target sequence into his own genome.
He is then able to gorge himself on pizza without digestive problems, and he's still able to do so several months later.
The adeno-associated virus is like a retrovirus, except that, per [0], the AAV will insert at a particular location in the genome, instead of at random locations.
Summary: Guy is lactose intolerant. He inserts a sequence providing lactose tolerance into an adeno-associated virus. He then infects himself with this virus, which inserts the target sequence into his own genome.
He is then able to gorge himself on pizza without digestive problems, and he's still able to do so several months later.
The adeno-associated virus is like a retrovirus, except that, per [0], the AAV will insert at a particular location in the genome, instead of at random locations.
[0] https://www.wikiwand.com/en/Adeno-associated_virus