Mitochondrial DNA Inheritance

[Steve Scadding]

Most of the literature I have read implies that mitochondrial DNA is 
inherited solely through the female line and is passed on via 
mitochondria in the egg. However, I recall having seen photographs which 
seem to show sperm mitochondria entering the egg.  This raises a lot of 
questions in my mind.
a) Is there clear evidence that sperm mitochondria do enter the egg?
b) If so, what is the fate of these mitochondria?  Are they destroyed by 
the egg cell or do they survive and contribute to the mitochondrial 
complement of the zygote?
c)  Is the maternal inheritance of mitochondrial DNA simply a dilution 
phenomenon?  I.e., the quantity of paternal mitochondrial DNA may be so 
small as to be undetectable.
I would greatly appreciate it if anyone could point me to recent reviews 
of this area or other literature bearing on these question.
Thanks very much.
..Steve Scadding