Chapter 2, Problem 11EQ

A recessive allele in mice results in an unusally long neck. Sometimes, during early embryonic development, the long neck causes the embryo to die. An experimenter began with a population of true-breeding normal mice and true-breeding mice with long necks. Crosses were made between these two populations to produce an ${\text{F}}_{\text{1}}$ generation of mice with normal necks. The ${\text{F}}_{\text{1}}$ mice were then mated to each other to obtain an ${\text{F}}_{\text{2}}$ generation. For the mice that were born alive, the following data were obtained:

522 mice with normal necks

62 mice with long necks

What percentage of homozygous mice (that would have had long necks if they had survived) died during embryonic development?