Final answer:
Increased predisposition for dementia pugilistica is noted in individuals with defects on chromosome 17, where the apolipoprotein E (APOE) gene, specifically the E4 variant, is located.
Step-by-step explanation:
The predisposition for dementia pugilistica is increased in carriers with defects on chromosome 17. This is because the apolipoprotein E (APOE) gene, which has a variant known as E4, is located on chromosome 19. This E4 variant increases the likelihood of Alzheimer's disease, which shares some pathological features with dementia pugilistica. Dementia pugilistica is a form of neurodegenerative disease that is often associated with repetitive brain trauma, such as that experienced by boxers. Carrying the defective gene on chromosome 17 may thus confer increased risk for the development of this type of dementia.