Page 143 - Science Course 3 (Book 1)

Mo4-L2b: What are the Patterns of Inheritance?

Complex Patterns of Inheritance Key Concept

Sometimes traits appear to be blends of alleles. What are the Patterns of Inheritance?
Alleles show incomplete dominance when the
offspring’s phenotype is a blend of the parents’ How does polygenic inheritance differ from
phenotypes. Mendel’s model?

Codominance occurs when both alleles can be
observed in a phenotype.

Red
RR

Incomplete Codominance
dominance

Yellow
rr

Some traits, such as human ABO blood type, are Genes and the Environment
determined by more than one allele.
An organism’s environment can affect its
Human ABO Blood Type phenotype.
Phenotype Possible Genotype Some examples of environmental factors that
affect phenotype are soil type that a flower is
Type A |A|A| or IAi growing in or time of year that a butterfly develops.

Type B |B|B| or IBi
Phenotype
Type O ii

Type AB |A|B

Polygenic inheritance occurs when multiple genes
determine the phenotype of a trait. Genes Environment

Skin color and eye color are examples.
SUMMARY

What are the Patterns of Inheritance?

Geneticists use Punnett squares to predict
the possible genotypes and phenotypes of
offspring.

In polygenic inheritance, traits are
determined by more than one gene and have
many possible phenotypes

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