Section 7-2Section 7-2“Complex “Complex

InheritanceInheritance””

Write everything that isWrite everything that is BLACKBLACK

7.2 Complex Patterns of Inheritance

KEY CONCEPT KEY CONCEPT Phenotype is affected by many different factorsPhenotype is affected by many different factors

7.2 Complex Patterns of Inheritance

Phenotype can depend on interactions of allelesPhenotype can depend on interactions of alleles

• Incomplete dominanceIncomplete dominance: neither allele is : neither allele is completely dominant nor completely completely dominant nor completely recessiverecessive

–Heterozygous phenotype is Heterozygous phenotype is intermediate between the two intermediate between the two homozygous phenotypeshomozygous phenotypes

7.2 Complex Patterns of Inheritance

• CodominantCodominant alleles will both be alleles will both be completely expressedcompletely expressed

–Codominant Codominant alleles are neither alleles are neither dominant nor dominant nor recessiverecessive

– The ABO blood The ABO blood types result from types result from codominant codominant allelesalleles

• Many genes have more than two allelesMany genes have more than two alleles

7.2 Complex Patterns of Inheritance

• How can two people with type How can two people with type B B blood have a child blood have a child with type with type OO blood? blood?

• If two people are heterozygotes (If two people are heterozygotes (IIBi) they can each they can each pass the recessive allele (pass the recessive allele (ii) to their offspring.) to their offspring.

7.2 Complex Patterns of Inheritance

Many genes may interact to produce one trait Many genes may interact to produce one trait

• PolygenicPolygenic traits traits are produced by are produced by two or more two or more genesgenes

Order of dominance: Order of dominance: brown > green > blue.brown > green > blue.

7.2 Complex Patterns of Inheritance

• An epistatic gene can interfere An epistatic gene can interfere with other genes with other genes

An epistatic gene blocks the production of pigments.

7.2 Complex Patterns of Inheritance

• How do multiple allele traits differ from polygenic How do multiple allele traits differ from polygenic traits?traits?

• Multiple allele traits are influenced by several Multiple allele traits are influenced by several different versions of one gene; polygenic traits are different versions of one gene; polygenic traits are influenced by multiple genesinfluenced by multiple genes

7.2 Complex Patterns of Inheritance

The environment interacts with genotypeThe environment interacts with genotype• Phenotype is a Phenotype is a combination of genotype combination of genotype and environment and environment •The sex of sea turtles The sex of sea turtles depends on both genes depends on both genes and the environmentand the environment•Height is an example of a Height is an example of a phenotype strongly phenotype strongly affected by the affected by the environmentenvironment

Warm = femaleWarm = female

Cold = MaleCold = Male

7.2 Complex Patterns of Inheritance

• Sunlight can cause a person’s hair to become lighter Sunlight can cause a person’s hair to become lighter in color. Is this an example of an interaction between in color. Is this an example of an interaction between genes and the environment? Why or why not?genes and the environment? Why or why not?

• Yes, because the phenotype is altered by the Yes, because the phenotype is altered by the environment.environment.