Page 151 - 86 human physiology part-2

Chapter 18

• STD's,
• Aids,
• Parasites,

Sensitive period to teratogen exposure, in the embryonic period is most vital. Fetal damage is
minor.

Genetic Engineering

Genetic Engineering is where the DNA or gene gets changed by a scientist to make a gene with the
characteristics that they want it to have, and to get rid of the characteristics that they don't want the
gene to have. This process can be applied towards any plant, animal, or person.

The main reason for genetic engineering is to "mass produce" a certain protein. Each cell is
responsible for producing a certain protein and these proteins can be used for medical treatment and
diagnosis. The job of each gene is to control the production of a particular protein in a living cell. If the
gene responsible for synthesizing a important or useful protein can be found, and if that gene can be
inserted into another cell that can be made to reproduce, then a colony of cells containing that gene can
be grown and the protein will be manufactured in large quantities. This process is responsible for
insulin and growth hormones and it is also used in vaccines to help prevent hepatitis and a treatment to
help prevent viral infections. It also helps in genetically engineering Factor VIII which is a treatment
for hemophilia.

The first step is to find the gene in the DNA of a cell that is responsible for the manufacturing of
the desired protein. Then that gene is either extracted or the exact chemical structure is figures out to be
synthesized. The last step is to insert the DNA into the recipient which is done by using special
enzymes to split a molecule of the recipients cell and inserting the new gene.

There have been many steps taken to bring technology closer to being able to fix genetically
inherited diseases. Hopefully someday there will be a lot less babies born with genetic diseases and
disorders.

Gene Therapy

Gene therapy is a way to correct the defective genes that are the cause of disease development.
When the genes are altered proteins are not able to function normally and as a result of this, defects can
occur. Current gene therapy is still being experimented with, but in some cases it is very effective.

Genes are carried on chromosomes and are the basic physical and functional parts of hereditary.
When there is a genetic disorder, gene therapy can help fix the problem either permanently or at least
temporarily. The most common form of gene therapy is to insert a gene into a nonspecific place to
replace a malfunctioning gene. Another method is gene swapping, where an abnormal gene is replaced
by a normal gene. Genes could also be repaired through "selective reverse mutation" which returns the
gene to it's original function. The degree to which a gene is turned on or off can also be altered.

Gene therapy works on the principle belief that a virus genome can be manipulated to remove
disease causing genes and new therapeutic genes can be inserted in their place. These new genes are

366 | Human Physiology