unrelated parents 1st cousins difference Observed 0.04 0.11 007 frequency of still birth or neonatal death Average number of recessive lethals in both grandparents =0.07/0.016=4.4 Thus each grandparent has an average of 2. 2 recessive lethal allelesunrelated parents 1st cousins difference Observed 0.04 0.11 0.07 frequency of still￾birth or neonatal death Average number of recessive lethals in both grandparents = 0.07/0.016 = 4.4 Thus each grandparent has an average of 2.2 recessive lethal alleles