A curious polymorphism in human populations has to do with the ability to curl up the sides of the tongue to make a trough (“tongue rolling”). Some people can do this trick, and others simply cannot. Hence, it is an example of a dimorphism. Its significance is a complete mystery. In one family, a boy was unable to roll his tongue but, to his great chagrin, his sister could. Furthermore, both his parents were rollers, and so were both grandfathers, one paternal uncle, and one paternal aunt. One paternal aunt, one paternal uncle, and one maternal uncle could not roll their tongues.a. Draw the pedigree for this family, defining your symbols clearly, and deduce the genotypes of as many individual members as possible.b. The pedigree that you drew is typical of the inheritance of tongue rolling and led geneticists to come up with the inheritance mechanism that no doubt you came up with. However, in a study of 33 pairs of identical twins, both members of 18 pairs could roll, neither member of 8 pairs could roll, and one of the twins in 7 pairs could roll but the other could not. Because identical twins are derived from the splitting of one fertilized egg into two embryos,

A curious polymorphism in human populations has to
do with the ability to curl up the sides of the tongue to
make a trough (“tongue rolling”). Some people can do
this trick, and others simply cannot. Hence, it is an example of a dimorphism. Its significance is a complete
mystery. In one family, a boy was unable to roll his
tongue but, to his great chagrin, his sister could.
Furthermore, both his parents were rollers, and so were
both grandfathers, one paternal uncle, and one paternal
aunt. One paternal aunt, one paternal uncle, and one
maternal uncle could not roll their tongues.
a. Draw the pedigree for this family, defining your
symbols clearly, and deduce the genotypes of as many
individual members as possible.
b. The pedigree that you drew is typical of the inheritance
of tongue rolling and led geneticists to come up with the
inheritance mechanism that no doubt you came up with.
However, in a study of 33 pairs of identical twins, both
members of 18 pairs could roll, neither member of 8 pairs
could roll, and one of the twins in 7 pairs could roll but
the other could not. Because identical twins are derived
from the splitting of one fertilized egg into two embryos,