Download Notes Gen. Bio cont Objectives: 1. Identify the similarities and

Notes Gen. Bio cont
Objectives:
1.
Identify the similarities and differences between multiple allele and polygenic traits and cite an
example of each kind of trait.
2.
Recognize blood type as a multiple allele traits and be able to make predictions using your newly
acquired genetic skill set i.e ( be able to work problems with blood type) .
3.
Articulate the reasons for differences in blood type using appropriate vocabulary i.e. (
agglutination, immunoglobulin, antibody, antigen, proteins, etc)
Multiple allele traits vs Polygenic traits
Polygenic traits are those traits that have more than one gene that controls them. Each of those genes
would then have it’s own set of alleles. For example, a persons foot size is not limited by just one gene.
There are many genes that contribute to the foot size of an individual. Each of those genes have
alternate alleles that may or may not be phenotypically expressed.
Multiple allele traits
M. A . traits are those traits that have a single gene that limits the trait, but have more than two alleles
like we are used to dealing with. For example, eye color was treated as a problem with one gene and
two alleles. The brown and blue alleles and brown was dominant to blue. Blood type is a multiple allele
trait. There is only one gene that controls blood type but it has three alternate forms. Allele A, B and i(
we use the letter “I” for allele O. Thus geneotypes are AA or Ai for type a blood. BB or Bi for type B
blood , ii for type O blood and AB for type AB blood. Note that A and B alleles are co-dominant to each
other and dominant to the i allele.
Blood type .
Blood types are different from one another based on not only different genotypes, but also on the way
the red blood cells look and the type of proteins ( immunglobulins or antibodies) that are in the blood
plasma. For example, type A blood has type A proteins ( immunoglobulins or antigens) on the red
blood cells, but it also has Type B proteins in the plasma of that blood. Plasma is the liquid portion of
the blood and not the red blood cells themselves. Likewise, Type B blood has type B proteins on the red
blood cell , but type A proteins in the plasma. If you give Type A blood to a Type B person. The
proteins in the plasma from the Type A person will adhere to the proteins on the red blood cells of the
type B person and a clumping of blood be form that resist flow through blood vessels. We call this
clumping agglutination. A type AB person has both protein types on RBC’s and no antibodies of A or B
in the plasma. A type O person has no protein types on the RBC’s and both antibodies in the plasma.
A typical problem example might look like the following:
A woman with type A blood marries a man with type B blood and they have a child with type O blood.
What are the genotypes of the parents? The easiest way to solve this is to work a couple of punnent
squares and decide what it is not.
Mom could be genotype AA or Ai and still have type A blood.
Dad could be genotype BB or Bi and still have type B blood.
B
B
A
ii
A
As you can see above, there is no way for mom and dad to be homozygous for their blood type and wind
up with a child that has type O blood. Assuming fidelity in the relationship, they would both have to be
heterozygous for their blood type to wind up with a type O child.