Set
Cornell
Notes
on pg.
6.5 up
Traits
and
Probability
85
Patterns
2.17.2
Atoms,
Ions, of Inheritance
and Molecules
•Topic: 7.2 Patterns of
Inheritance
1. Why might polygenic traits vary more in
•Essential Questions:
1. Why might polygenic
traits vary more in
phenotype than do
single-gene traits?
2. How is codominance
the same as having no
dominant and recessive
relationship at all
between 2 alleles?
phenotype than do single-gene traits?
2. How is codominance the same as
having no dominant and recessive
relationship at all between 2 alleles?
KEY CONCEPT
Phenotype is affected by
many different factors.
6.5 Traits and Probability
84
Incomplete Dominance
Codominance
7.2 Complex Patterns of Inheritance
KEY CONCEPT
Phenotype is affected by many different factors.
7.2 Complex Patterns of Inheritance
+
• What are our possible outcomes for this combination of flower
color?
• What if red nor white was dominant or recessive to one another?
7.2 Complex Patterns of Inheritance
• In incomplete dominance, neither allele is completely
dominant nor completely recessive.
• They are a BLEND of each other
• Ex: red+white rose= pink rose
BB
RR
BR
7.2 Complex Patterns of Inheritance
– Heterozygous phenotype is intermediate between
the two homozygous phenotypes
– Homozygous parental phenotypes not seen in F1
offspring
Green betta fish
(GG)
Steel blue betta fish
(BB)
Royal blue betta fish
(GB)
7.2 Complex Patterns of Inheritance
B
B
BR
BR
BR
BR
R
R
Genotype: BR
Phenotype: 100% pink flowers
7.2 Complex Patterns of Inheritance
B
B
R
R
BB
BR
Red rose
Pink rose
BR
RR
Pink rose
White rose
Genotype:
BB, RR, BR
Phenotype: 25%= red flowers
50%= pink flowers 25%= white flowers
7.2 Complex Patterns of Inheritance
• Codominant alleles will both be completely expressed.
– Codominant
alleles are
neither
dominant nor
recessive.
Ex: multi-colored
red and white rose
Ex: In humans, ABO blood type. (A, B, AB, O)
7.2 Complex Patterns of Inheritance
B
B
BR
BR
BR
BR
R
R
Genotype: BR
Phenotype: 100% red and white flowers
7.2 Complex Patterns of Inheritance
B
R
BB
BR
BR
RR
B
R
Genotype: BB, BR, RR
Phenotype: 25% red flowers, 50% red-white flowers,
25% white flowers
7.2 Complex Patterns of Inheritance
How to tell if we are asking you about incomplete
dominance OR codominance..
The trick is to recognize when you are dealing with a
question involving incomplete dominance. There are two
steps to this:
• 1) Notice that the offspring is showing a 3rd
phenotype. The parents each have one, and the
offspring are different from the parents.
• 2) Notice that the trait in the offspring is a blend (mixing)
of the parental traits.
• Polygenic
traits
are produced
by two
7.2
Complex
Patterns
of Inheritance
or more genes.
– Can produce a continuous range
of colors
Ex: Skin color- 4-6 genes
Eye color- at least 3 genes
7.2 Complex Patterns of Inheritance
Sponge Bob Incomplete Dominance Worksheet