1. 10.3 Polygenic Inheritance (and More…) Learning Targets: I can define and give examples of polygenic inheritance. I can review blood groups, pedigrees, and sex-linked traits.

2. Polygenic – two or more genes affect a phenotype – these traits usually vary on a continuum Ex) human height, human skin color

3. Traits with a limited number of phenotypes show discontinuous variation. Traits with a wide range of phenotypes show continuous variation.

4. Ex. Skin Color -The skin pigment melanin protects against damaging UV rays in intense sunlight -Some UV light must penetrate skin to produce vitamin D for bone growth What strategies allow people to protect themselves from UV rays and get sufficient vitamin D, regardless of where they live? Sunscreen for places with intense sun, vitamin D supplements for areas without enough sun

5. Multiple Alleles – more than two alleles exist for a trait Ex) human blood groups have A (I A ), B (I B ) and O (i) alleles, A and B are codominant, O is recessive GenotypePhenotype I A I A, I A i I B I B, I B i IAIBIAIB ii

6. GenotypePhenotype I A I A, I A i Type A Blood I B I B, I B i Type B Blood IAIBIAIB Type AB Blood iiType O Blood

7. Sex-linked Traits – traits controlled by alleles on the X or Y chromosome – males have XY chromosomes, females have XX chromosomes. Ex) hemophilia is a recessive blood-clotting disease, carried on the X chromosome (X h ) Cross a normal male with a carrier female – X H Y x X H X h How many of their children will have hemophilia?

8. Cross a hemophiliac male with a normal female – How many of their children will have hemophilia?

9. Pedigree – a family tree showing the occurrence of a certain trait Circles represent females; squares represent males; shaded shapes indicate individuals who show the trait of interest.

10. Individual 11 is ( male / female). Individual 11 (shows / doesn’t show ) the trait of interest. If the trait is dominant, what is #11’s genotype? ______ If the trait is dominant, what is #1’s genotype? ______

11. Individual 11 is ( male / female). Individual 11 (shows / doesn’t show ) the trait of interest. If the trait is dominant, what is #11’s genotype? __aa__ If the trait is dominant, what is #1’s genotype? Aa