Muggle-borns

[Tandra]

No: HPFGUIDX 168046

Is there an explanation anywhere as to why or how Muggleborns come to be?  I'm not sure I worded that right but basically if you have no magic parents why do they have kids that are magical?  Also is it a hereditary thing?  If one child is will they all be? In the case of the Creeveys it seems so.  So that would lead us to believe that Petunia has possible powers but refuses to use or acknowledge them?  Any opinions or just information for me that I might not have? Thx :-)

Tandra