Multiple Alleles
Genetics Unit
Biology 30
Mrs. S. Pipke-Painchaud
Multiple Alleles
• have 3 or more alleles for the same gene (or at
a single locus)
• In Other Words – there are 3 or more alleles that
create the different traits.
• at most one individual will have 2 alleles or 1
pair (unit factors exist in pairs.)
• in a species, however, many alternative forms
exist
Example – ABO Blood Group
• this deals with the presence of antigens
– These are like labels/ name tags on the blood
cells.
• Each individual has 1 of 4 phenotypes
– Type A
– Type B
– Type AB
– Type O
– What are you?
The Info You Need To Know
• Gene designated is I (isoagglutinogen)
– I = A antigen
– I = B antigen
– i = no antigen
•
IA
IB
and are both
codominant
• IA and IB are both
dominant to I
(type O)
Genotype
IAIA
IAi
IBIB
IBi
IAIB
ii
Antigen
A
A
B
B
AB
Neither
Phenotype
A
A
B
B
AB
O
• http://learn.genetics.utah.edu/units/basics/blood/types.cfm
Website Resoures
• Nobel Prize – Blood Typing Website:
– http://nobelprize.org/educational_games/medicine/landsteiner/rea
dmore.html
– View for animations and background info on blood types.
• Wikipedia – Blood Types
– http://en.wikipedia.org/wiki/Blood_type
– Contains a chart of blood types by nation.
• Maps of the Distribution of Human Blood Types all over
the World.
– http://anthro.palomar.edu/vary/vary_3.htm
• Sickle Cell Anemia Example:
– http://www.astrographics.com/GalleryPrintsIndex/GP2146.html
Did You Know?
• B is the rarest allele.
• 16% of the population have it.
– Distribution of Blood Types
• http://anthro.palomar.edu/vary/vary_3.htm
http://www.uwosh.edu/med_tech/teachin
g/ElementaryHemeWeb/LEARN%20AB
http://www.faqs.org/health/i
• Wikipedia: http://en.wikipedia.org/wiki/Image:ABO_blood_type.svg
Practice
• If a person with Type
A (Heterozygous)
blood married and
had children with a
person who has Type
B (Heterozygous)
blood, what would the
genotypic and
phenotypic ratios be?
– I Ai X
I Bi
IA
i
IB
IAIB
IBi
i
IAi
ii
Genotypic Ratio:
1 IAIB : 1 IAi: 1 IBi: 1 ii
Phenotypic Ratio:
1 AB: 1 A: 1 B: 1 O
Practice
• If you crossed a person
with type 0 with
heterozygous type B,
what would the
phenotypic ratio be?
– ii X IBi
– Phenotypic Ratio:
• 1B:1O
i
i
IB
IBi
IBi
i
ii
ii
Website Resoures
• Nobel Prize – Blood Typing Website:
– http://nobelprize.org/educational_games/medicine/lan
dsteiner/readmore.html
– View for animations and background info on blood
types.