 However, homozygotes for recessive lethal mutations are , per definition , non-viable, which necessitates maintenance of the mutation in heterozygous organisms . Crosses between heterozygotes yield a wild-type organisms , in addition to hetereozygotes and the non-viable homozygotes.
<fluency>  However, homozygotes for recessive lethal mutations are , per definition , non-viable, which necessitates maintenance of the mutation in heterozygous organisms . Crosses between heterozygotes yield a wild-type organisms , in addition to hetereozygotes and the non-viable homozygotes.
 However, homozygotes for recessive lethal mutations are , per definition , non-viable, which necessitates maintenance of the mutation in heterozygous organisms . Crosses between heterozygotes yield wild-type organisms , in addition to hetereozygotes and the non-viable homozygotes.