Infection of tumor cells with conditionally replicating adenovirus results in tumor-specific replication,subsequent oncolysis and release of the virus progeny.
Individuals crossing exclusively within the same population produce more progeny than those crossing in both directions and thereby use up some of their gametes for the production of inviable hybrids.
A single bull named Jackson (pictured above) has sired many of the calves born in the United States in the past decade, and scientists say new bloodlines are needed to avoid future inbreeding among his many progeny.