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 fire-

power alleles F (strong fire) and F’ (no fire) that follow incomplete dominance, what are the phenotypes for the following dragon-fire genotypes?– FF : - F’F’– FF’

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 fire-

power 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 - F’F’: no fire– FF’: some 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 FF’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 FF’ 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 FF’ 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

flowerIn 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

flowerIn 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 BGG

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 BG BG BGG BG BG

Codominance

• If 2 Merpeople with blue and green tails have merbabies, what are the phenotypes and genotypes of the children?

B G

BG

Codominance

• If 2 Merpeople with blue and green tails have merbabies, what are the phenotypes and genotypes of the children?

B G

B BB BGG 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 GB BB BGG BG GG

Multiple Alleles

• Multiple alleles have more than 2 variations • EX: human blood types have 3 different allele

variants, A, B and OGenotypes Phenotypes

AA, AO A blood type

AB AB blood typeBB, BO B blood type

OO 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 O

B

B

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:

A OB AB BOB 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-

A OB AB BOB 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 Pigment

eeBb, eebb, eeBB

EEbb, Eebb

EEBB, EeBB, EEBb, EeBb

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 G

B

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:• Harry’s phenotype:

Xn YXNXN

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 YXN XNXn XNYXN XNXn XNY

To close out the genetics unit, I hope you have had fun with the Harry Potter theme, enjoy this wrap upWhat do the kids of Ron and Hermonie and Harry and Ginny actually look like?