What is Codominance?
Codominance
• Occurs when both alleles for a gene are
expressed in a heterozygous individual.
Roan Cattle
Codominance
• There are two alleles for coat color in cattle.
• Yet, there are three phenotypes:
A combination of red and white hairs!
Codominance
• Since both alleles are DOMINANT, a
capital letter is used for both alleles!
WW
RR
WR
Let’s do some Monohybrid Crosses!
Cross a RED cow with
a WHITE bull
X
Codominance
Cross a Roan cow
with a Roan bull
X
Let’s Think…
A cross between a black cat & a tan cat produces a tabby
pattern (black & tan fur together).
a) What pattern of inheritence does this illustrate?
Codominance, two phenotypes
together at the same time.
b) What percent of kittens would have tan fur if a tabby cat
is crossed with a black cat?
What are Multiple Alleles?
• Traits controlled by 3 or more alleles of the
same gene that code for a single trait.
ABO Blood Types
Blood Type contains three alleles:
Genotype
Blood Type
IA I A
IA i
IB I B
IB i
IA I B
ii
A
A
B
B
AB
O
A
B
I ,I ,
i
Here is another example of Codominance:
Both the IA allele and the IB
allele are expressed!
Let’s Try some Blood Typing Crosses!!!
A husband and wife have the ABO
blood group genotypes IAIB and ii.
What ABO blood types can their
children have?
Let’s Try some Blood Typing Crosses!!!
A husband and wife have the
ABO blood groups IBi and IAi.
What ABO blood types can their
children have?
What is blood made up of?
•
•
An adult human has about 4–6
liters of blood circulating in the
body. Among other things, blood
transports oxygen to various parts
of the body.
Blood consists of several types of
cells floating around in a fluid
called plasma.
The red blood cells contain
hemoglobin, a protein that binds
oxygen. Red blood cells transport
oxygen to, and remove carbon
dioxide from, the body tissues.
The white blood cells fight
infection.
The platelets help the blood to
clot, if you get a wound for
example.
The plasma contains salts and
various kinds of proteins.
BLOOD FACT
• In the United
States, a blood
transfusion is
needed about every
two seconds.
DID YOU KNOW?
• When someone donates a
pint of blood, that blood
is separated into red
cells, plasma and
platelets.
• Each one of these can be
given to a different
patient who needs only
that part of the blood.
BLOOD TYPE
• Not everyone has the
same blood type!
• Blood type refers to
features of the
person’s red blood
cells.
So what’s the deal with
Blood Transfusions?
Located on the surface of red blood cells!
• Located in the plasma
Blood Transfusions
A blood transfusion is a procedure in which blood is given to a patient through an
intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace
blood lost during surgery or a serious injury. A transfusion also may be done if a person’s
body can't make blood properly because of an illness.
Who can give you blood?
Universal Donor
People with TYPE O blood are called
Universal Donors, because they can give
blood to any blood type.
People with TYPE AB blood are called
Universal Recipients, because they can
receive any blood type.
Rh +  Can receive + or Rh -  Can only receive Universal Recipient
Rh Factors
•
•
•
Scientists sometimes study Rhesus monkeys to learn
more about the human anatomy because there are
certain similarities between the two species. While
studying Rhesus monkeys, a certain blood protein was
discovered. This protein is also present in the blood of
some people. Other people, however, do not have the
protein.
The presence of the protein, or lack of it, is referred to
as the Rh (for Rhesus) factor.
If your blood does contain the protein, your blood is
said to be Rh positive (Rh+). If your blood does not
contain the protein, your blood is said to be Rh
negative (Rh-).
http://www.fi.edu/biosci/blood/rh.html
A+ AB+ BAB+ ABO+ O-
How common is your blood type?