How are witches and wizards made?

Some Background Info…

The story of Harry Potter is set in a world like our own.

This world is populated by people with magical powers (wizards and witches) and a majority of people without any powers (muggles).

Wizards or witches can be of any race, and may be the offspring of:– a wizard and a witch (pureblood aka

purebred)– the offspring of two muggles (muggle-born)– or of mixed ancestry (half-blood aka hybrid).

This suggests that wizarding ability is an inherited trait, with the magic allele (m) being recessive and the nonmagic allele being dominant (M).

M=non-magic allelem=magic allele

All witches and wizards have the alleles mm.

All muggles have the alleles MM or Mm.

Lily Potter mm

James Potter mm

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

The Potters

mmThey passed these alleles on to Harry.

mm Harry Potter

The Malfoys

Lucius Malfoy mm

Narcissa Malfoy mm

The Malfoys are a ‘pure blood’ family.

Draco Malfoy

All their ancestors are wizards so they must have the alleles mm.

mm

The Weasleys

The Weasleys are pure blood wizards so they all have the alleles mm.

And what about Hermione?Hermione is a powerful

witch but both of her

parents are muggles…they must be Mm to

pass on the magic allele…

Mr. Granger MmMrs. Granger Mm

Hermione Granger

mm

VoldemortHe is a half blood… his mother was a witch

and his father a muggle.

mm

Tom Riddle, Sr. Mm Merope Gaunt mm

Voldemort

Filch…

Filch is a squib…he has NO powers even though BOTH of his parents are wizards (mm).

How could this happen?

Now for some problems….

?

Ron Weasley and Hermione Granger end up married. What chance is there that their children will be witches and wizards?

Lets work through the problem…1. We start with a four square box… a Punnett square.

2. We place the genotype (alleles) of the parents on the outside of the box…

3. Then we combine them together to get the possibilities of the children…

m m

m

m

mm mm

mm mm

There is a 100% chance that Ron and Hermione’s kids will be witches or wizards.

mm

What about Harry Potter and Ginny Weasley? Because they are a witch and wizard, the

outcome would be the same as it was for Ron and Hermione.

mm

mm

So…

let’s imagine that Ginny, instead of marrying Harry, married JUSTIN BIEBER! And let’s say Justin’s genotype is MM. Remember, Ginny’s genotype is mm.

m

m

M M

Mm Mm

Mm Mm

What chance is there that Justin and Ginny’s kids will be witches or wizards?

ZERO!

If Hermione had brothers and sisters what chance is there that they would be witches and wizards?

The genotype for both of Hermione’s parents in Mm. We know this because they produced Hermione who is mm.

M m

M

m

MM

mmMm

Mm

Mr. and Mrs. Granger have a:

25% Chance of having a witch or wizard

75% chance of having a muggle