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

7.2 Complex Patterns of Inheritance

KEY CONCEPT Phenotype is affected by many different factors.


Phenotype can depend on interactions of alleles.

• In incomplete dominance, neither allele is completely dominant nor completely recessive.– Heterozygous phenotype is intermediate

between the two homozygous phenotypes• Heterozygous is like a “blend”


Example: Cross a homozygous red carnation flower (RR) with a homozygous white flower (WW).

• List the genotypes.

4RW

• List the phenotypes.

4 Pink


Example: Cross one heterozygous pink (RW) 4 o’clock flower with a White flower (WW).


2RW, 2WW

• List the phenotypes.

2 Pink, 2White

7.2 Complex Patterns of InheritanceCodominance• 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


• 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

• Many genes have more than two alleles.


Ex: Cross Jason who is homozygous for type A blood with Maria who is homozygous for type B blood.


4AB• List the phenotypes.

4 type AB blood


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 blood1 type A blood1 type B blood1 type o blood

• Probability of Heterozygous individual?75%


Many genes may interact to produce one trait.

• Polygenic traits are produced by two or more genes.

Order of dominance: brown > green > blue.


• An epistatic gene can interfere with other genes.• This is like a “knock out” gene


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.