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

7.2 Complex Patterns of Inheritance In (3.)incomplete dominance, (AKA- intermediate dominance) neither allele is completely dominant nor completely recessive. Heterozygous phenotype is intermediate between the two homozygous phenotypes Use capital letters and apostrophes’ RR-red homozygous dominant RR’-pink heterozygote is intermediate R’R’-white homozygous recessive

7.2 Complex Patterns of Inheritance

Phenotype can depend on interactions of alleles. In (3.)incomplete dominance, neither allele is completely dominant nor completely recessive. –Heterozygous phenotype is intermediate between the two homozygous phenotypes –Homozygous parental phenotypes not seen in F 1 offspring –B 1 B 1 Green B 2 B 2 blue B 1 B 2 royal blue

7.2 Complex Patterns of Inheritance (4)Codominant –equal expression of both alleles. –Codominant alleles are neither dominant nor recessive. Ex. The ABO blood types result from codominant alleles. Ex. Sickle cell disorder RR- normal red blood cell shape RS-sickle cell trait- carrier SS-sickle cell anemia

7.2 Complex Patterns of Inheritance Genetic disorder- Hemoglobin- a protein in Red Blood Cells that carry oxygen to body cells Sickle cell anemia-a genetic disorder that causes a change in the shape of red blood cells Sickle cell Trait-some normal, some sickle shaped cells

7.2 Complex Patterns of Inheritance

(5) multiple alleles Traits that are controlled by more than 2 alleles, although only two alleles exist in a diploid cell. Example- Human Blood Types-each person inherits two alleles, one from each parent, but three exist in the human “gene pool”. 4 blood types 3 alleles Type-AI A I A, I A i A is dom. to O Type-BI B I B, I B iB is dom. To O Type-ABI A I B AB are codominant Type-Oiirecessive This is determined by the shape of proteins on red blood cells and by the presence or absence of plasma antigens. O universal donor-AB universal receiver.

7.2 Complex Patterns of Inheritance (6)Polygenic -many genes may interact to produce one trait. The genes may be on the same or on a different chromosome. Result in a wide range of variation. Ex. Hair color, height eye color Order of dominance: brown > green > blue.

7.2 Complex Patterns of Inheritance Often compared to a bell curve AA,BB,CChighest range aa.bb.cclowest range Aa,Bb,Ccmiddle

7.2 Complex Patterns of Inheritance An (7)epistatic gene can interfere with other genes.

7.2 Complex Patterns of Inheritance Other factors of gene expression Phenotype is a combination of genotype and environment. Ex.Height is an example of a phenotype strongly affected by the environment. Ex.The sex of sea turtles depends on both genes and the environment- (temperature of the nest) External environment- temperature, nutrition, light Internal factors: different hormones, structures, and effects of aging.