Transcript Blood Typing - LawBiology11

Blood Typing
Agenda:
Hand in the 3 incomplete dominance questions
Spotlight
Multiple Alleles
How is blood type determined?
Blood Transfusions
Solving basic blood typing questions.
Review of Last Class
What is the difference between
incomplete and co-dominance?
 In co-dominance both alleles are
expressed fully. Both parental phenotypes
can be distinguished in the offspring
 In incomplete dominance, both alleles are
expressed to an extent, producing an
intermediate phenotype.

What if a woman who was heterozygous
for sickle cell anemia decided to have a
baby with a man, who was homozygous
for sickle cell anemia?
 HbSHbN x HbSHbS
 What would the F1 generation be?
 What are the chances their child will have
sickle cell anemia?

Multiple Alleles

The traits we have been studying so far,
have all been controlled for by one gene
with two alleles (eg. eye colour or flower
colour. )
Multiple Alleles
Many traits in humans and other species
are the result of the interaction of more
than two alleles for one gene.
 These multiple forms of genes are
referred to as multiple alleles
 An individual can only ever have two
alleles for each gene.
 But in the population many different
alleles can exist.

Blood Type
An example of a trait controlled for by
multiple alleles on one gene, is blood type.
 What are the possible blood types?
 Do you know what blood type you are?
 How do you know this?

What Does Blood Type Refer To?
In humans, a single gene determines a
person’s ABO blood type.
 This gene and its alleles, determine what
type of antigen molecule, if any, is attached
to the cell membrane of red blood cells.
 It is the presence of these antigens, which
determine your blood type.

Type A blood contains A antigen
 Type B blood contains B antigen

Type AB blood contains both A and B
antigens
Type O blood contains neither antigen

There are three alleles coding for antigens
on the red blood cell membrane.
 The alleles can be represented by IA, IB
and Ii
 Recall from last class, the big letter
represents the gene coding for the trait
 While the superscript letters represent
the alleles.

What can you conclude about the A, B and i alleles?
Which ones are recessive, dominant and co-dominant to each
other?

Type A blood has these genotypes: IAIA, IAIi

Type B blood has these genotypes: IBIB, IBIi

Type AB blood has this genotypes: IAIB

Type O blood has this genotype: IiIi
 IA and IB
alleles are dominant over Ii allele.
 IA and IB alleles are co-dominant because
both alleles are expressed simultaneously.
Practice Problem
Imagine a mom, who is heterozygous for
blood type A had a child with her
husband, who is homozygous for blood
type B.
 What would the probability of having a
child with blood type A?
 With blood type AB?
 With blood type B?

What is an antigen?
An antigen is a substance or molecule
that when introduced into the body
triggers the production of an antibody by
the immune system.
 An antigen acts a marker for cells.
 The antibody, will then kill or neutralize
the antigen that is recognized as a foreign
and potentially harmful invader.

Antibodies

Take the next minute to read the chart
and fill in the blanks
What Do Antibodies Do?
What would you do?
Imagine you are on a hiking trip and you cut
yourself very badly.You are losing a large
amount blood very quickly. Your friend
suggests to transfuse (donate) some blood
to you (so you do not pass out or DIE),
while you are both waiting for help.You are
blood type A and your friend has a blood
type of B.
 Should you accept your friend’s generous
offer? Take a minute and discuss with a
partner

Blood Transfusions

If you went ahead with the blood transfusion.
Your anti-B antibodies would react with the B
antigens from your friend’s blood. Causing the
red blood cells to burst and/or clump together
and block vessels.

Incorrect transfusions can be fatal!
Test Your Understanding of blood groups by
completing the table below:



With a partner take 2 minutes to complete the table
What blood type would be considered the universal
donor?
What blood type would be considered the universal
recipient?
Therefore, blood type AB are universal
recipients
 Blood type O are universal donors!

Practice Problem
From our earlier problem, what
percentage of the mother’s children
would be able to donate blood to her?
 What about the father?

Summary
Blood type is controlled for by one gene
and the interactions between 3 alleles
 Blood type refers to the antigen present
on the membrane of red blood cells.
 Your body produces antibodies to
antigens, not present inside of you. These
antibodies clot red blood cells.
