2. 7.2 Complex Patterns of Inheritance KEY CONCEPT Phenotype is affected by many different factors.

3. 7.2 Complex Patterns of Inheritance Phenotype can depend on interactions of alleles. Autosomal dominance –Only need to inherit one copy of the disorder to be affected –Disease is dominant (DD or Dd) –Homozygous dominant: early death, usually don’t survive to reproduce –Heterozygous: live into adulthood –Healthy is recessive (dd) –Ex: Familial hypercholesterolemia (also called FH) or Huntington’s disease

4. 7.2 Complex Patterns of Inheritance Usually 50/50 chance of inheriting autosomal dominance due to only 1 parent being affected

5. 7.2 Complex Patterns of Inheritance Autosomal Dominance Inheritance Ex: Paul has familial hypercholesterolemia and Stacy is healthy. The two have 3 children, 2 boys, and a girl. After testing, the middle child is the only healthy child. Key F = FH f = healthy disease healthy PaulStacy Ff ff

6. 7.2 Complex Patterns of Inheritance Another example… Huntington’s disease is a dominant disorder found on chromosome 4. Betty and Marcus met at a support clinic they have been attending to help them cope with the knowledge of their illness with Huntington’s disease. They would like to know the risk of having a healthy child, now that Betty is pregnant. Key H = Huntington’s disease h = healthy diseasedisease diseasehealthy MarcusBetty Hh ?

7. 7.2 Complex Patterns of Inheritance Incomplete Dominance neither allele is completely dominant nor completely recessive. –Heterozygous phenotype is intermediate between the two homozygous phenotypes Heterozygous is like a “blend”

8. 7.2 Complex Patterns of Inheritance Example: Cross a homozygous red carnation flower (RR) with a homozygous white flower (WW). List the genotypes. 4RW List the phenotypes. 4 Pink

9. 7.2 Complex Patterns of Inheritance Example: Cross one heterozygous pink (RW) 4 o’clock flower with a White flower (WW). List the genotypes. 2RW, 2WW List the phenotypes. 2 Pink, 2White

10. 7.2 Complex Patterns of Inheritance Codominance Defined: When both alleles are dominant and equally expressed The colors do NOT blend together, but are equally seen Ex: Cattle Coat Red cow x White cow = Roan Cow Ex: Human Blood types Type A x Type B = Type AB

11. 7.2 Complex Patterns of Inheritance Blood types are another example of codominance. –The ABO blood types result from codominant alleles –This blood group consists of 3 different alleles Dominant A allele Dominant B allele Recessive O allele A and B are equally dominant

12. 7.2 Complex Patterns of Inheritance Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood. List the genotypes. 4AB List the phenotypes. 4 type AB blood

13. 7.2 Complex Patterns of Inheritance Ex: Cross Mike who is heterozygous for type A blood with Lisa who is heterozygous for type B blood. List the genotypes. 1AB, 1Ao, 1Bo, 1oo List the phenotypes. 1 type AB blood 1 type A blood 1 type B blood 1 type o blood Probability of Heterozygous individual? 75%

14. 7.2 Complex Patterns of Inheritance Many genes may interact to produce one trait. Polygenic traits are produced by two or more genes. Order of dominance: brown > green > blue.

15. 7.2 Complex Patterns of Inheritance An epistatic gene can interfere with other genes. This is like a “knock out” gene

16. 7.2 Complex Patterns of Inheritance The environment interacts with genotype. Height is an example of a phenotype strongly affected by the environment. The sex of sea turtles depends on both genes and the environment Phenotype is a combination of genotype and environment.