Bellringer 10/29
1. In rabbits, white fur color (W) is dominant to black, and
long ears (L) are dominant to short. Draw a Punnett
square that represents the cross between two rabbits
heterozygous for both traits. What are the phenotype
and genotype ratios?
2. In humans, polydactylism (having an extra finger on
each hand) is dominant to the typical 5-finger
arrangement. Tongue rolling is dominant to not being
able to roll one’s tongue. A man who is homozygous for
5-fingers and who cannot roll their tongue has children
with a woman who is heterozygous for polydactylism
and tongue rolling. Draw a Punnett square that
represents the cross. What is the probability the
couple will produce a polydactyl baby who cannot roll
their tongue?
In rabbits, white fur color (W) is dominant to black, and long
ears (L) are dominant to short. Draw a Punnett square that
represents the cross between two rabbits heterozygous for
both traits. What are the phenotype and genotype ratios?
In humans, polydactylism (having an extra finger on each hand) is
dominant to the typical 5-finger arrangement. Tongue rolling is dominant
to not being able to roll one’s tongue. A man who is homozygous for 5fingers and who cannot roll their tongue has children with a woman who
is heterozygous for polydactylism and tongue rolling. Draw a Punnett
square that represents the cross. What is the probability the couple will
produce a polydactyl baby who cannot roll their tongue?
Beyond Mendel
Mendelian Inheritance (aka complete dominance)
When one trait is clearly dominant over
another.
Mendel was very fortunate that all the pea
plant traits that he studied exhibited complete
dominance.
Incomplete Dominance
When neither allele is dominant over the
other
The heterozygote’s phenotype is a BLEND
of the two homozygous phenotypes.
P generation  red x white
RR x WW
Genotypes:
Phenotypes:
F1 generation  pink x pink
_______ x _______
Genotypes:
Phenotypes:
Genotypic ratio:
Phenotypic ratio:
Codominance
When neither allele is dominant over the
other BOTH alleles show up in the
heterozygote
P generation  black x white
BB x WW
Genotypes:
Phenotypes:
Blood types are also codominant.
Antigen A
Antigen A & B
Antigen B
AB blood type x AB blood type
___________ x __________
Genotypes:
Phenotypes:
Genotypic ratio:
Phenotypic ratio:
Incomplete Dominance or
Codominance?
Birds can be
blue, white, or
white with bluetipped feathers.
Flowers can be
white, pink, or
red.
A bleexco can be
spotted, black,
or white.
A sneech can be
tall, medium, or
short.
A Hoo can have
curly hair,
spiked hair, or a
mix of curly and
spiked hair.
Multiple Alleles  when three or more alleles
code for one trait
ex: blood type has three alleles
(O is recessive)
Genotype
IAIA (AA)
IAi (AO)
IBIB (BB)
IBi (BO)
IAIB (AB)
ii (OO)
Phenotype
A
A
B
B
AB
O
Homozygous male type B x heterozygous female type A
___________ x ___________
Genotypes:
Phenotypes:
Genotypic ratio:
Phenotypic ratio:
Male type O x female type AB
___________ x ___________
Genotypes:
Phenotypes:
Genotypic ratio:
Phenotypic ratio:
If a boy has a blood type O and his sister has
blood type AB, what are the genotypes and
phenotypes of their parents?
Sex-linked Traits / X-linked Traits
Located on the X chromosome (NOT Y!)
Examples: hemophilia, color blindness
Trait: Hemophilia
H = no hemophilia h = hemophilia
(normal male) x (female carrier)
XHY
x
HH = no hemophilia
Hh = no hemophilia
Hh = hemophilia
XY = male
XX = female
XHXh
Most sex-linked, recessive traits – including
hemophilia and color blindness – appear in
males. This phenomenon is best explained by
which statement?
A. Males have an X chromosome with dominant
genes.
B. Most of the genes on the X and Y
chromosomes of males are recessive.
C. In males, the recessive sex-linked genes
appear only on the Y chromosome.
D. In males, the Y chromosome lacks the genes
needed to mask the recessive genes on the X
chromosome.
A couple has five children, all with blood type
A. The mother’s blood type is O, and the
father’s blood type is A. Based on this
information, which describes the most
probable genotype of the father?
A.
B.
C.
D.
Diploid
Haploid
Heterozygous
Homozygous
Some flowers show incomplete dominance. If
RR = white and R’R’ = red, which phenotypic
ratio would be expected in the offspring of
two pink flowers?
A.
B.
C.
D.
1 red : 2 pink : 1 white
0 red : 4 pink : 0 white
3 red : 0 pink : 1 white
4 red : 0 pink : 0 white
Are you Finished?
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Worksheet Complete? Correct?
Vocabulary?
Missing work?
Quiz on Wednesday (11.4)
– All content fair game
• Test moved to the 6th
• See me! =)