The Genetics of Short Sleepers: What defines a short sleeper?

What defines a short sleeper?
 
They can function well on 6 hours of sleep or less.
 

Part B
While it is estimated that less than 5% of the population are short sleepers,
 
an estimated 30% of the population sleep only 6 hours per night or less.
 

Part C
The risks of sleep deprivation include ____.
 
 
all of the above

Part D
The discovery of a gene associated with short sleepers means that
 
there is potential to manipulate sleep pathways with medication.

Part E
Since there is a genetic explanation for short sleepers, you would expect
 
 
that this trait appears more frequently among family members.