Prions are misfolded proteins with the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals.
In a mammalian brain, there are four major lobes that are present and one of them is the frontal lobe.
The frontal lobe is mainly rich in dopaminergic neurons and thus, it is mainly concerned with functions such as memory, reward, motivation, planning, attention, etc.
The process of break down of tissues and cell death in the tissues is referred to as atrophy and since the frontal lobe is associated with the functions as mentioned above its atrophy would lead to a slow decline in these functions.
Since Mr. Klondlike behavior is changing his blunt comments are most likely a result of atrophy of the frontal lobe.
To find the probability we can draw a 4-square Punnett square using the parents' alleles for the gene. If you want a more detailed explanation I would be glad to help :)
