Transcript Luckily Ginny ends up with Harry.

Harry Potter
and the
Recessive Allele
How Are Wizards Made?
How Are Wizards Made?
• Being a wizard or a muggle is all decided by genetics.
This outward reflection of a characteristic is called the
phenotype.
• All humans including wizards receive one allele from
each parent. These alleles are called the genotype of a
person.
How Are Wizards Made?
• The allele for wizarding ability is recessive and symbolized
by m
• Wizards therefore have the homozygous alleles mm
How Are Wizards Made?
• The allele for muggleness is dominant and represented by M
• Muggles have the alleles Mm or MM
• M is dominant to m so you can only be a wizard if you have
no M allele
The Malfoys
Narcissa Malfoy
(mm)
Lucius Malfoy (mm)
Draco Malfoy
m( m)
The Malfoys are a ‘pure blood’ family
All their ancestors are wizards so they must have the alleles mm
The Potters
James Potter (mm)
Lily Potter (mm)
Harry Potter (WW)
mm
Even though Lily Potters heredity is mudblood (mixed blood from wizard:mm and
muggle:Mm parents) she along with James Potter had magical ability so they must both
have been mm.
They passed these alleles on to Harry
The Weasleys are pure blood wizards so they all have the alleles mm
Hermione is a powerful witch so she must be mm
Mm
Mm
mm
Both her parents are muggles so they must each be Mm so they can give
her a m allele each
Tom Riddle is a ‘half blood’.
His mother was a witch (mm) and his father was a muggle
His father must have had the alleles Mm so he could give him the other m allele
Mm
mm
mm
Filch is a ‘squib’
Both his parents are mm so he should be too because he can’t get an M allele from either
parent - but he can’t do any magic
This means he has a mutation so his wizarding powers don’t work or the man he thinks is
his father isn’t really and his mother had an affair with a muggle who was Mm!
Probability
Probability = the number of times an event is expected to happen
Number of opportunities for an event to happen.
Using a diagram called a
Punnet Square we can
figure out the probability of
different crosses and
predict breeding results.
What wizarding alleles would Ron and Hermione’s children have?
Ron (mm)
Hermione
(mm)
Children
m
( m)
Their children could only get
the m allele from both
parents so they would all be
wizards
Ron
m
m
m
mm
mm
m
mm
mm
Hermione
What wizarding alleles would Ginny and Dudley’s children have if Dudley was homozygous
dominant?
If Dudley is MM
Ginny mm
Children
M
mWM
Dudley MM
Their children would get the
m allele from Ginny and the
M allele from Dudley so they
would all be muggles
Dudley
M
M
m
M
mWM
M
mWM
m
M
mWM
M
mWM
Ginny
What wizarding alleles would Ginny and Dudley’s children have if Dudley was heterozygous? If
Dudley is Mm
Ginny mm
Children
m MWW or mM
m m
Dudley Mm
Half of their children would be likely to get the
m allele from both parents so they would be
wizards
The other half would be likely to get an M allele
from Dudley and would be muggles.
Luckily Ginny
ends up with
Harry.
Dudley
m
M
m
m m
m M
m
m m
m M
Ginny
What wizarding alleles would you
expect Hermione’s
brothers and sisters to have?
The Granger’s children have a one in four chance of getting
m alleles from both parents and having magical ability
They also have a one in four chance of getting M alleles
from both parents and being a muggle
Mr Granger
They could also get only one m from their mother or father
and an M from the other and still be a Muggle but a carrier
of wizardry.
m
M
m
m
m WW
M
mWM
M
M
mWM
M
M MM
Mrs Granger
The Magic of Genetics
Gregor Mendel, not a wizard, but a very smart guy with pea plants.
1. Recessive and Dominant Traits
Alleles that are dominant mask the recessive
allele factor for a specific trait.
2. Segregation
Alleles are separated during the formation of
gametes (eggs and sperm) during meiosis.
3. Independent Assortment
Different traits are distributed independently.
Just because an organism is dominant in one
trait it does not affect the other traits.
…
Genetics
Not all characteristics are as simple as wizardry. Some have many alleles that determine
a trait. Others are codominant or incomplete.
Some traits are passed along by the sex chromosomes X and Y and are called sex linked
characteristics.
We are still gaining knowledge of how genetics work.
Even Harry Potter would have something to learn.