Hans Nachtsheim investigated an inherited anomaly of white blood cells in rabbits. He has arrested the segmentation of the nuclei of white cells. This anomaly does not appear inconvenience, for the rabbits.
a) Pelger crossed with normal stock, which has resulted in two phenotypes in 1:1 ratio (pelger or heterozygous (A/a - normal) and homozygous (a/a - recessive). This problem states that it is normal is true breeding or a/a. therefore, pelger must be A/a.
b) Three phenotypes could arise on crossing two pelger rabbits. This shows that the anomaly of pelger is dominant to normal. An expected ration of 1:2:1 is expected when a cross is made between A/a X A/a. Since, the normal is a/a the extremely abnormal progeny should be A/A (which would die even before birth).
c) The pelgar allele is lethal, when it is homozygous and is dominant, for nuclear segmentation of white blood cells in a heterozygous. The non-surviving fetuses could look, for as in a homozygous allele there would be one-fourth reduction in the litter size. This litter size could be studied extensively by comparing it with normal x normal with pelger x pelger.
d) The absence of homozygous pelger anomaly in humans could be expressed as recessive lethal allele on comparing it with rabbits. During random mating, it should be noted that one of the four progeny would be expected to have the lethal recessive progeny. Thus, homozygous pelger anomaly is expected in only 1 of 4 million births which is extremely rare.
e) Two-thirds would be expected to show pelger anomaly and one third would be normal. The remaining one third possess the homozygous lethal allele and are not supposed to survive till birth.