Harry Potter and the recessive characteristic Wizards and muggles, its in the

genes

Wizard or muggle?

Being a wizard or a muggle depends on genetics

Characteristics are determined by genes that are found on chromosomes

Individuals have two sets of chromosomes, one set from the mother the other set from the father

Therefore for a particular gene each individual will have two copies, one from the mother and one from the father

chromosomes

gene

from motherfrom father

Wizard or muggle?

Genes can have different forms called alleles, eg wizard allele or muggle allele

The muggle allele is assigned the letter ‘M’ and the wizard allele is assigned ‘m’

It is this combination that determines whether you are a wizard or a muggle

To be a wizard you must have mm

A muggle can have MM or Mm

Muggle allele (M)

Wizard allele (m)

Wizard or muggle?

The Malfoys are a “pure-blood” family

All their ancestors are wizards and therefore they only have mm

The Malfoys

Lucius Malfoy

Narcissa Malfoy

Draco Malfoy

(mm)

(mm)

(mm)

Wizard or muggle?

Both Harry’s parents had magical ability, so they must both have been mm

Harry will have received an ‘m’ from each parent

The Potters

Lily Potter (mm)

James Potter (mm)

Harry Potter

(mm)

Wizard or muggle?

They are all pure-bloods so they all have mm and are wizards

The Weasleys

Wizard or muggle?

Hermione is a witch with powerful magical abilities but she does not come from a pure-blood family

Neither of her parents had magical abilities

What were her parents’ genes?

They must have both been Mm

Hermione Granger (mm)

Mm

Mm

mm

Wizard or muggle?

Tom riddle is “half-blood”

His mother had magical abilities but his father was a muggle

What combination of alleles must Tom’s father have?

Tom Riddle (mm)

Mm

mm

mm

father mother

Wizard or muggle?

Filch is a “squib”

Both his parents were wizards and therefore mm

This means that Filch must also be mm but he has no magical abilities

Why is this so?

One possibility is that he has a mutation that has resulted in the genes not working

Another possibility is that some environmental factor has affected his wizard genes working

Or is his father really his father? Hmmm…

Argus Filch (mm)

Wizard or not?

Wizard or muggle?

What if Ron and Hermione got together?

What sort of children would they have?

Ron (mm)

Hermione (mm)

children (mm)

We can use a punnet square to predict the characteristics of the next generation (offspring)

The alleles of each parent are placed on the sides

Wizard or muggle?

Ron (mm)

Hermione (mm)

m

m

m m

mm mm

mm mm

All children must be mm!

All the different combinations are worked out

Remember only one allele is passed on, but it is totally random and each has the same chance

GENOTYPE is the combination of alleles eg Mm or mm or MM

PHENOTYPE is the characteristic that we observe eg muggle or wizard

HOMOZYGOUS is when both the alleles are the same eg MM or mm

HETEROZYGOUS is when the two alleles are different eg Mm

PURE-BREED is another word for homozygous

HYBRID is another word for heterozygous

DOMINANT is the trait you see when either type of allele is present-muggle

RECESSIVE is the trait you see only when both alleles are the same type-wizard

Wizard or muggle? Some

terminology

Wizard or muggle?

Ginny Weasley

(mm)

Dudley Dursley (MM)

What if Ginny and Dudley got together? What would their children be like?

Dudley is related to Harry but is definitely not a wizard. He is homozygous.

children (?)

Ginny will only be able to pass on ‘m’

Dudley will only be able to pass on ‘M’

Wizard or muggle?

Dudley (MM)

Ginny (mm)

m

m

M M

Mm Mm

Mm Mm

All children (100%) will be heterozygous and muggles!

Wizard or muggle?

What wizarding alleles would you expect Hermione’s brothers and sisters to have?

Remember Hermione is a “muggle-born”. What must her parents have been?

They both must have been heterozygous.

Mr Granger (Mm)

Mrs Granger

(Mm)

M

m

M m

MM Mm

Mm mm

¾ (75% chance) would be a muggle

¼ (25% chance) would be a wizard