The Genetics of DifferenceTHE MEANING OF HERITABILITY (H)

IMPORTANT FACTS ABOUT HERITABILITY– THE PROPORTION OF THE TOTAL

VARIANCE IN A TRAIT THAT IS ATTRIBUTABLE TO GENETIC VARIATION WITHIN A GROUP• MAX VALUE IS 1.0• HEIGHT HAS A HIGH H

•APPLIES ONLY TO A PARTICULAR GROUP IN A PARTICULAR ENVIRONMENT•DOES NOT APPLY TO INDIVIDUALS, ONLY VARIATIONS WITHIN GROUPS• EVEN HIGHLY HERITABLE TRAITS CAN BE MODIFIED BY ENVIRONMENT (MALNUTRITION AND WT./HT.)

• http://www.youtube.com/watch?v=bsdHDTIPPU8

COMPUTING HERITABILITY•ADOPTION STUDIES–SHARE ½ GENETIC MAKE UP, BUT NOT ENVIRONMENT–CORRELATIONAL COMPARISON BETWEEN TRAITS OF PARENTS AND KIDS–ATTEMPT TO SEPARATE ENVIRONMENTAL FROM GENETIC FACTORS

• TWIN STUDIES–COMPARE SAME SEX

FRATERNAL TWINS WITH GROUPS OF IDENTICAL TWINS– ID TWINS MORE ALIKE EQUALS

HIGH H–TO AVOID SOCIAL BIAS, ID

TWINS THAT WERE SEPARATED ARE BEST (see BOUCHARD & LYKKEN)