Download ABO Blood Type: An Example of Genetic Variation

ABO Blood Type: An Example of Genetic Variation
• Humans have two
copies of an
enzyme that
makes
carbohydrates that
stick off of the red
blood cell plasma
membrane.
• In some humans
this enzyme has a
structure that
causes it to make
A type
carbohydrates.
ABO Blood Type: An Example of Genetic Variation
• In others this enzyme
has a structure that
causes it to make B
type carbohydrates.
• In others they may
have copies of both
enzyme structures.
• In still others this
enzyme has a
structure that makes
in nonfunctional so no
carbohydrate is
made.
How can one enzyme have so
many different possible
structures?
Let’s look at how these protein
enzymes are made: from DNA to
mRNA to Protein…
The Flow of Genetic Information
from DNA to RNA to Protein
– DNA functions as the inherited directions
for a cell or organism.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
From Nucleotides to Amino
Acids: An Overview
– Genetic
information in
DNA is
transcribed into
RNA and then
translated into
polypeptides
(proteins).
The Genetic Code
How does a change in the
DNA code affect the structure
of a protein?
ABO Blood Type: An Example of Genetic Variation
• So the ABO gene
has
– different DNA
sequences that
code for the
– different protein
enzyme structures
that makes one of
these
– different types of
carbohydrates.
Genetic Variation!!!
– The immune system produces antibodies!
• These may cause clotting when blood cells of a
different type enter the body.