Harry Potter and the not so
simple world of genetics
Rules of Inheritance
• Some traits follow the simple rules of
Mendelian inheritance of dominant and
recessive genes.
• Complex traits follow different patterns of
inheritance that may involve multiple genes
and other factors. For example:
– Incomplete domiance
– Codominance
– Multiple alleles
– Polygenic inheritance
Incomplete dominance
• Incomplete dominance results in a phenotype
that is a blend of a heterozygous allele pair.
• Ex: red flower + blue flower = purple flower
• If the dragons in Harry Potter have the firepower alleles F (strong fire) and F’ (no fire)
that follow incomplete dominance, what are
the phenotypes for the following dragon-fire
genotypes?
– FF :
– FF’
- F’F’
Incomplete dominance
• Incomplete dominance results in a phenotype
that is a blend of a heterozygous allele pair.
• Ex: red flower + blue flower = purple flower
• If the dragons in Harry Potter have the firepower alleles F (strong fire) and F’ (no fire)
that follow incomplete dominance, what are
the phenotypes for the following dragon-fire
genotypes?
– FF : strong fire
– FF’: some fire
- F’F’: no fire
Practice problems for incomplete dominance
• If a Hungarian Horntail (strong fire) is mated
with a Peruvian Vipertooth (no fire) what will
the offspring have in terms of its fire power?
Practice problems for incomplete dominance
• If a Hungarian Horntail (strong fire) is mated
with a Peruvian Vipertooth (no fire) what will
the offspring have in terms of its fire power?
F
F’
F’
F
Practice problems for incomplete dominance
• If a Hungarian Horntail (strong fire) is mated
with a Peruvian Vipertooth (no fire) what will
the offspring have in terms of its fire power?
F’
F’
F
FF’
FF’
F
FF’
FF’
Practice problems for incomplete dominance
•
•
If a Hungarian Horntail (strong fire) is mated with a Peruvian Vipertooth (no fire)
what will the offspring have in terms of its fire power?
Phenotypes:
–
–
–
Strong fire:
Some fire:
No fire:
F’
F’
F
FF’
FF’
F
FF’
FF’
Codominance
• Codominance results in a phenotype that
shows both traits of an allele pair.
– Ex: red flower + white flower = Red and white spotted
flower
In Harry Potter, there are merpeople who live in Black Lake
that is around the school. The Merpeople have tail colors
that are codominant between green and blue. Their
possible genotypes and phenotypes are:
Genotypes:
Phenotypes:
Codominance
• Codominance results in a phenotype that
shows both traits of an allele pair.
– Ex: red flower + white flower = Red and white spotted
flower
In Harry Potter, there are merpeople who live in Black Lake
that is around the school. The Merpeople have tail colors
that are codominant between green and blue. Their
possible genotypes and phenotypes are:
Genotypes:
Phenotypes:
– BB
blue tail
– GG
green tail
– BG
blue & green tail (both traits)
Codominance
• If a merman with a blue tail meets a mermaid
with a green tail and they have merbabies,
what are the possible genotype and
phenotype frequencies?
Codominance
• If a merman with a blue tail meets a mermaid
with a green tail and they have merbabies,
what are the possible genotype and
phenotype frequencies?
B
G
G
B
Codominance
• If a merman with a blue tail meets a mermaid
with a green tail and they have merbabies,
what are the possible genotype and
phenotype frequencies?
G
G
B
BG
BG
B
BG
BG
Codominance
• If 2 Merpeople with blue and green tails have
merbabies, what are the phenotypes and
genotypes of the children?
B
B
G
G
Codominance
• If 2 Merpeople with blue and green tails have
merbabies, what are the phenotypes and
genotypes of the children?
B
G
B
BB
BG
G
BG
GG
Codominance
• If 2 Merpeople with blue and green tails have
merbabies, what are the phenotypes and
genotypes of the children?
•
•
•
•
Phenotypes:
Blue:
Green:
Blue and green:
B
G
B
BB
BG
G
BG
GG
Multiple Alleles
• Multiple alleles have more than 2 variations
• EX: human blood types have 3 different allele
variants, A, B and O
Genotypes
Phenotypes
AA, AO
AB
A blood type
BB, BO
OO
AB blood type
B blood type
O blood type
Multiple Alleles: Human Blood types
• If Lily and James have A (AO) and B (BB) blood
types, what are the possible genotypes and
phenotypes of their children?
Multiple Alleles: Human Blood types
• If Lily and James have A (AO) and B (BB) blood
types, what are the possible genotypes and
phenotypes of their children?
A
B
B
O
Multiple Alleles: Human Blood types
• If Lily and James have A (AO) and B (BB) blood
types, what are the possible genotypes and
phenotypes of their children?
A
O
B
AB
BO
B
AB
BO
Multiple Alleles: Human Blood types
• If Lily and James have A (AO) and B (BB) blood
types, what are the possible genotypes and
phenotypes of their children?
– Phenotypes:
•
•
•
•
A:
B:
AB:
O:
B
B
A O
AB BO
AB BO
Multiple Alleles: Human Blood types
• If Lily and James have A (AO) and B (BB) blood
types, what are the possible genotypes and
phenotypes of their children?
– Genotypes:
• AB• BO-
B
B
A O
AB BO
AB BO
Epistasis
• One allele masks the effects of another
• Ex: Dudley has a labrador retriever.
(Dudley is so mean he
stays in the doghouse for the whole series though)
• In labs, the dominant allele (E) determines
whether the skin will have pigment. The
dominant allele (B) determines how dark it is.
Epistasis
•
•
•
One allele masks the effects of another
Ex: Dudley has a labrador retriever. (Dudley is so mean he stays in the doghouse for the whole series though)
In labs, the dominant allele (E) determines whether the skin will have pigment. The dominant allele (B) determines how
dark it is.
Genotype
eeBb, eebb, eeBB
EEbb, Eebb
EEBB, EeBB,
EEBb, EeBb
Pigment
Polygenic Inheritance
• More than one pair of genes influencing a trait
• Examples:
– skin color (approx 3 but discussion of more)
– eye color
– Height
Polygenic Inheritance
•
•
More than one pair of genes influencing a trait
Examples:
– skin color (approx 3 but discussion of more)
– eye color
– Height
Hagrid’s father was a wizard and his mother was a
giantess. The normal heights are approxiamtely
20 feet for a giant and 5-6 feet for a wizard.
Hagrid is approximately 12 feet tall.
Polygenic Inheritance
•
More than one pair of genes influencing a trait
Eye color in humans is polygenic inheritance,
but it has multiple alleles.
B=brown (codominant with green)
G= green (codominant with brown)
b= blue (recessive to both brown and green)
Assuming Lily has green eyes (GG) and James has hazel (BG)
what will their children have?
Polygenic Inheritance
•
More than one pair of genes influencing a trait
Eye color in humans is polygenic inheritance, but it has multiple alleles.
B=brown (codominant with green)
G= green (codominant with brown)
b= blue (recessive to both brown and green)
Assuming Lily has green eyes (GG) and James has hazel (BG)
what will their children have?
G
B
G
G
Polygenic Inheritance
•
More than one pair of genes influencing a trait
Eye color in humans is polygenic inheritance, but it has multiple alleles.
B=brown (codominant with green)
G= green (codominant with brown)
b= blue (recessive to both brown and green)
Assuming Lily has green eyes (GG) and James has hazel (BG) what will their
children have?
Hazel:
Green:
G
G
B
BG
BG
G
GG
GG
Sex-Linked Traits
• 46 chromosomes in the human body: set into
23 pairs (22 pairs of autosomes and 1 pair of
sex chromosomes).
• In most animals, the sex chromosomes are X
and Y chromosomes with the Y being smaller
(X is longer than the Y)
• Male: XY
• Female: XX
Sex-Linked Traits
• Male determines the sex of the offspring
• Chance is 50-50 for either sex
• A recessive gene has no matching gene on the
Y chromosome. More sex linked disorders are
found in males.
Sex linked traits
• In a calico cat, the X’s that control the different
colors are turned on in different cells, reason
for the black and orange pigments (so only girl
calico cats!)
• Harry had a calico cat when he was a baby
that Voldemort killed when he killed Harry’s
parents
Sex linked traits
• Sex-linked disorders are those that are carried
on the X chromosome.
• Examples are:
– Red-green colorblindness
– Baldness
– Hemophillia
Sex-linked traits
• So if Harry is colorblind and married Ginny
who is not, what are the chances that they will
have a colorblind child?
• Ginny’s phenotype:
• Harry’s phenotype:
Sex-linked traits
• So if Harry is colorblind and married Ginny
who is not (and neither are her parents), what
are the chances that they will have a
colorblind child?
• Ginny’s phenotype:
Xn Y
• Harry’s phenotype:
XN
XN
Sex-linked traits
• So if Harry is colorblind and married Ginny
who is not (and neither are her parents), what
are the chances that they will have a
colorblind child?
•
•
•
•
•
Colorblind girls:
Colorblind boys:
Carrier girls:
Normal Girls:
Normal Boys:
Xn
XN
XN
XNXn
Y
XNY
XNXn
XNY
To close out the genetics unit, I hope you have had fun
with the Harry Potter theme, enjoy this wrap up
What do the kids of Ron and Hermonie and Harry and Ginny actually look
like?