On Wed, 29 Jul 2009 10:44:12 -0400, kurt <[log in to unmask]> wrote:
>but I think it's highly speculative to say that significant changes
>can be passed from a complex multicellular organism like an insect or
>a mammal to offspring which are the result of sexual recombination of
>genetic material. 

Sexual reproduction involves a bit more than just the recombination of DNA. Many other 
substances are present in the egg and sperm and may have a variety of functions, 
including improving the viability of the offspring.

* * *

Recently it has been demonstrated that, along with sperm, some of its RNA can be 
introduced into the oocyte during fertilization, which stays stable until the activation of 
the embryonic genome. Originally it was thought that RNA present in semen relates to 
contamination from somatic cells and/or immature sperm both containing substantially 
higher amounts of RNA than the fertilizing sperm. 

Pooled human sperm contains about 5000 different mRNA sequences of which half are 
common between ejaculates. Besides mRNA sperm also contains small sperm RNA 
molecules that might interfere in gene expression (iRNA). In human sperm already more 
than 68 putative iRNAs have been identified and 15 of them may specifically inhibit genes 
that are only active during early embryonic development. 

The composition and quantity of sperm RNA is considered to be a valuable diagnostic tool 
for male fertility. However, only a subpopulation of the purified mature sperm fraction 
(with a yet unknown composition and quantity of RNA) will appropriately respond to 
capacitation media to become competent to fertilize the oocyte.

A possible role for sperm RNA in early embryo development
Theriogenology, Volume 68, Issue null, Pages S147-S155
A. Boerke, S. Dieleman, B. Gadella

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