Question

Look at the data below and explain what they say about the genetic and environmental influence on each characteristic. How did you interpret these data? (MZ = monozygotic twins and DZ = dizygotic twins.)

Concordance in
Trait MZ DZ
Right- or left-handedness 80 75
Manic depression 80 20
a. Handedness and manic depression both have a strong genetic basis and little or no environmental basis.
b. Handedness and manic depression are both strongly affected by environmental factors with little or no genetic basis.
c. Handedness and manic depression are strongly affected by both environmental factors and genetic factors.
d. Handedness is strongly affected by environmental factors with little or no genetic basis, while manic depression is significantly affected by genetic factors.
e. Handedness is significantly affected by both environmental and genetic factors, while manic depression is significantly affected by environmental factors with little genetic basis.

Answer 1

The concordance data for twins suggest that handedness is influenced by both genetics and environment, while manic depression has a strong genetic basis. The higher concordance rate for handedness in DZ twins indicates environmental influence, and the stark difference in concordance rates between MZ and DZ twins for manic depression underscores a genetic etiology.

Step-by-step explanation:

The data indicating concordance rates for right- or left-handedness and manic depression in monozygotic (MZ) and dizygotic (DZ) twins provides insight into the genetic and environmental influences on these traits. Right- or left-handedness shows a concordance of 80% in MZ twins and 75% in DZ twins. This suggests that handedness is influenced by both genetic and environmental factors, as the high concordance in DZ twins indicates a substantial environmental effect. Meanwhile, manic depression exhibits an 80% concordance in MZ twins but only 20% in DZ twins, which indicates a strong genetic component to this condition because MZ twins, who share 100% of their genes, have a much higher rate of concordance than DZ twins.

Therefore, the correct interpretation of the data is that handedness is significantly affected by both environmental and genetic factors, while manic depression is significantly affected by genetic factors. The findings align with studies on behavioral genetics, which demonstrate that our personalities, preferences, and traits are influenced by a mix of both inherited genetics and our experiences in the environment.