By highlighting the chromatin and watching the changes it goes through at different stages of the fertilisation process, the scientists found that the pro-nucleus in ssame mutant is wound into a tight ball that could not interact with its female counterpart, the egg pro-nucleus.

This showed that there was a problem with the re-packaging process in the ssame mutant.

The researchers looked at the genetic makeup of the ssame mutant and identified what is known as a point mutation in the HIRA gene showing that HIRA is the gene responsible for chaperoning the assembly of the sperm pro-nucleus.

"This is one of the most crucial process that takes place in sexually reproducing animals," said Dr Karr who works in the Department of Biology and Biochemistry at the University of Bath.

"Sperm DNA has to undergo a complete transformation when it arrives in the egg cell so that it can properly join with the female pronucleus to form a new genetically complete the beginning of a new life.

"A slight mutation in the HIRA gene means that life does not even get started.

"Amazingly we still know relatively little about the structure of sperm DNA and the genetic processes involved in the most crucial early phases of reproduction."

Because of the particular type of histone protein used in the re-packaging of sperm DNA, the researchers believe that this process leaves its mark in the genome of the newly-formed organism.

This genetic marker could be a useful way of tracking the genetic material an offspring inherits from either their father or mother.

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Contact: Andrew McLaughlin
a.mclaughlin@bath.ac.uk
44-1-225-386-883
University of Bath
26-Oct-2005