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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 7.2 Complex Patterns of Inheritance 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 F1 offspring –B1B1 Green B2B2 blue B1B2 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 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-A I AI A, I Ai A is dom. to O • Type-B I BI B, I Bi B is dom. To O • Type-AB IAIB AB are codominant • Type-O ii recessive • 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,CC • aa.bb.cc • Aa,Bb,Cc highest range lowest range middle 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. •External environmenttemperature, nutrition, light •Internal factors: different hormones, structures, and effects of aging. Ex.The sex of sea turtles depends on both genes and the environment(temperature of the nest) •Ex.Height is an example of a phenotype strongly affected by the environment.