In birds, sex is determined by a zw chromosome scheme that is much like the typical xy scheme seen in humans and many other organisms, except that the system is reversed: males are zz (similar to xx in humans) and females are zw (similar to xy in humans). a lethal recessive allele that causes death of the embryo occurs on the z chromosome in pigeons. what would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female? a) 1: 1 male to femaleb) 3: 1 male to femalec) 1: 2 male to femaled) 2: 1 male to female