Concept 14 Mendelian genetics cannot fully explain human health and behavior.
Cross pure-bred pea plants to identify dominant flower color.
HI! Charles Davenport's Eugenics Record Office (ERO) had a lot of human pedigrees, which tracked many different traits. These pedigrees were usually obtained by field workers and students of genetics. This pedigree is adapted from one sent to the ERO in 1933 by a student at the University of Wyoming. Three generations of this family are shown (I, II, III). In the second generation there is a pair of twin boys. According to this pedigree, is the inherited trait sex-linked? Yes. No, both males and females can inherit this trait. No. That is correct. Both males (squares) and females (circles) can inherit this trait. According to this pedigree, how is this trait inherited? There isn't enough data for a conclusive answer. That is correct. This is a dominant trait. Dominant inheritance can explain this pedigree. Affected people inherit a dominant allele from the affected parent. This is a recessive trait. Recessive inheritance can explain this pedigree. Affected people inherit a recessive allele from each parent. Dominant or recessive inheritance can explain this pedigree. If the trait is dominant, then the father in I is heterozygous for the trait. If the trait is recessive, then the father in I is homozygous for the trait and the mother in I is heterozygous. If this is an inherited dominant trait, then what can you conclude about the twins? These are Siamese twins. No, you can't possibly tell if these are Siamese twins or not. These are fraternal, non-identical twins. That is correct. These are identical twins. No, if these were identical twins, they would share the same genetic makeup. If this trait is dominantly inherited, then these twins must be non-identical, fraternal twins. Identical twins have the same genetic makeup and would have had the same phenotype. This in fact is a pedigree tracking the "inherited" interest in carpentry. Can this pedigree be explained without using genetics? How? All of the following. That is correct. Interest in carpentry was encouraged as a hobby by family members. Family members often share similar hobbies and activities. "Interest" is subjective, and is not easily measured. A interest in carpentry may be defined as building a house or watching others work with wood. The experimenter was biased and trying to prove a point. This pedigree was sent in by a student of genetics. It is possible that he wanted to prove his case. A pedigree like this can be explained without using genetics. An "interest" in carpentry can be encouraged by other family members. An "interest" is also difficult to quantify. The student who worked on this pedigree could have "led" participants to the "correct" answer. With pedigree analyses like these, eugenicists attributed a lot of human behavior to the science of genetics.