Page 401 - Carrahers_Polymer_Chemistry,_Eighth_Edition

364 Carraher’s Polymer Chemistry

diseases take time to manifest themselves since it takes time for the number of replications to
increase to a “dangerous” length.
The Huntington scenario paints a sad picture for our ability to “cure” those with the disease. Are
we to modify each of chromosome 4s in the billions of cells in our brain and if so how. It is not the
sequence itself, but rather the length of the sequence that is the problem. All of us have some of
these repeat sequences and they are necessary for other essential activities.
While certain behavioral and nonbehavioral diseases are believed to be monogenic, diseases

such as the Huntington, cyctic fibrosis, Marfan, and Hirschsprung result in the specified disease, the
outward appearance or result (phenotype) of the disease varies between individuals. For instance,
for the Marfan syndrome, there is a level below which the mutant protein does not exhibit itself

in an outward manner. Most of these diseases have modifier genes that cause modifications in the
outward demonstration of the disease and play a key role in the clinical symptoms. Further, the
particular metabolic pathways are often varied with several of the steps being important and the
importance of each mechanistic pathway may vary with individual.
We are learning external ways to identify activities, actions, that may be related to our genome
makeup. One of these observations involves changes in the capacity of individuals to “learn” with
age. It appears that the ability to learn language, grammar precisely, decreases as we grow older
and is most apparent in children. Thus, ability to learn a language appears to be gene related.
There are genetic conditions that are related to our linguistic ability. One is the Williams syn-
drome where affected children have very low general intelligence, but have a vivid and loqua-
cious ability to use language chattering on in long and elaborate sentences. Thus, they have a
heightened ability to learn language. The Williams syndrome is caused by a change in a gene
found on chromosome 11.

Another genetic-related disease is known as specific language impairment (SLI) where individu-
als with general intelligence have lowered linguistic ability. SLI is believed to be related to a gene
found on chromosome 7.
Genes are related with all aspects of our lives. Someone has said we are what we eat. We can
extend this to say that we become what our genes do with what we eat. There is a group of genes
called apolipoprotein or APO genes. There are four basic types of APO genes interestingly know as
A, B, C, and E (no explanation for what happened to D; known as APOA, APOB, etc.). Here we will

focus on a specific gene that appears on chromosome 19 know as APOE. As we eat, the various food
parts are digested, broken down. Both fats and cholesterol are brought through our blood stream
by lipoproteins, some called very low-density lipoproteins (VLDLs). These fats and cholesterol are
brought to various parts of the body to act as fuel and building blocks. As some of the triglycerides
are delivered, the proteins now are called simply low-density lipoprotein, or LDL known to many
of us as “bad cholesterol.” After delivering the cholesterol, it becomes high-density lipoproteins
(HDL) also know to us as good cholesterol and then returns to the liver to be replenished with
cholesterol and fats. The APOE protein acts to affect the transfer between VLDL proteins and a
receptor on a cell that needs some triglycerides. APOB serves a similar role except in delivering
cholesterol. Thus, the presence and effectiveness of genes that code for the APO genes helps control
our weight and health affecting such items as buildup on our arteries.
APOE is unusual in that it is polymorphic having several versions. The three most common are
know as E2, E3, and E4. E3, deemed the best variety of APOE, is the most common in Europeans
with about 80% having at least one copy and about 40% with two copies. But about 7% have two
copies of the E4 gene, the worst variety, and they are at high risk of early heart disease. These trends
of APOE are geographical and correlate with the frequency of heart disease. Thus, the frequency
of E4 is about three times as high in Sweden and Finland as in Italy and the frequency of coronary
heart disease is also about three times as high in Sweden and Finland in comparison to Italy. On
a race basis, Orientals have the lowest frequency of E4 (ca 15%), with American blacks, Africans,
and Polynesians all having higher values of E4, about 40%. Diet also contributes so that while New
Guineans have a high frequency of E4, their diet is low in fats and they have a low incidence of

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