What the . . . Punnett!!!
• You and 1 partner:
1) Come up with a
hypothesis of how
this could be (“if”
and “then”)
2) Make a punnett
square to support
your hypothesis
3) Be able to defend
your hypothesis
Codominance and Incomplete
Dominance
Beyond Mendel
Mmmendel!
• Polygenic Inheritance
• Many genes code for that 1
trait
• Ex:
• Eye color,
• height, and
• skin color
Order of dominance:
brown > green > blue.
• Multiple Alleles
• If there are
more than two
different alleles
for that gene
in the gene pool.
• Example:
ABO blood type
(IA , IB and i).
Incomplete Dominance
• Definition: A situation in which one allele is
not completely dominant over another.
• The heterozygous phenotype is somewhere
in between the two homozygous phenotype.
Tricks of Incomplete Dominance
• 1) Letters we use are both capitals because
both are dominant!
• 2) The offspring show a third phenotype
• 3) The offspring show a blending of the
parental traits
BlahBlahBlah!!!
• Question: A cross between a blue
blahblah bird & a white blahblah bird
produces offspring that are silver. The
color of blahblah birds is determined by
just two alleles.
– 1) What are the genotypes of the parent
blahblah birds in the original cross?
– 2) What is/are the genotype(s) of the silver
offspring?
– 3) What would be the phenotypic ratios of
offspring produced by two silver blahblah
birds?
Codominance
• Definition: Situation in which both alleles
of a gene contribute to the phenotype of an
organism
– Often produces offspring known as “eminette”
Sickle Cell Anemia
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Codominant
A=normal, S=Sickle
AA = Normal – Malaria
AS = Hetero – No Malaria
SS = Sickle – No Malaria