The following table gives the percentage of twin pairs studied in which both twins expressed the same phenotype for a trait (concordance). Percentages listed are for concordance for each trait in monozygotic (MZ) and dizygotic (DZ) twins. Assuming that both twins in each pair were raised together in the same environment, what do you conclude about the relative importance of genetic versus environmental factors for each trait? Trait MZ % DZ % Blood types 100 66 Eye color 99 28 Mental retardation 97 37 Measles 95 87 Hair color 89 22 Handedness 79 77 Idiopathic epilepsy 72 15 Schizophrenia 69 10 Diabetes 65 18 Identical allergy 59 5 Cleft lip 42 5 Club foot 32 3 Mammary cancer 6 3

The following table gives the percentage of twin
pairs studied in which both twins expressed the same phenotype
for a trait (concordance). Percentages listed are
for concordance for each trait in monozygotic (MZ) and
dizygotic (DZ) twins. Assuming that both twins in each
pair were raised together in the same environment, what
do you conclude about the relative importance of genetic
versus environmental factors for each trait?
Trait MZ % DZ %
Blood types 100 66
Eye color 99 28
Mental retardation 97 37
Measles 95 87
Hair color 89 22
Handedness 79 77
Idiopathic epilepsy 72 15
Schizophrenia 69 10
Diabetes 65 18
Identical allergy 59 5
Cleft lip 42 5
Club foot 32 3
Mammary cancer 6 3