CHAPTER 14 GENE THERAPY GENES AND HUMAN GENOME

CHAPTER 14 GENE THERAPY

GENES AND HUMAN GENOME

Genome is a complete set of genes in a cell or organism. resides in 46 chromosomes that basically come in pair in from the father and another 23 from the mother. This chromosomes dictate the characteristics of an organism determined as dominant recessive. Human genome which 23 are pairs of and can be

- A chromosomes are made up of two chromatids and each chromatid contains sequence of DNA (deoxyribonucleic acid). - DNA commonly found in the nucleus of every cell. Genes are made up of hundreds of thousands of chemical bases. Not all the genes in the strand of DNA are working at the same time. For example, the genes that are “switched on” in the heart are different from those genes that are ‘switched on’ in the eye. The genes or portion of the DNA sequence that are coded to proteins are called introns and the non-coding regions are called exons.

Genetics Disorders Genetic disorders caused by abnormalities in the DNA sequence of an individual. These irregularities can happen in just one gene or there is an addition or subtraction of chromosomes. More than 4000 identified medical disorders that are caused by defective genes although genes are responsible for predisposition of these diseases, the environment, diet, and lifestyle are also factors that trigger these diseases. These genetic disorders are classified into single-gene disorder, chromosomal disorder and multifactorial inheritance.

Single-Gene Disorder Single Gene Disorder caused by mutation in specific genes. In humans, there are 50, 000 to 100, 000 estimated genes that are responsible for coding proteins which are needed by cells and tissues to perform its specific function. - Single genes disorders are classified in to autosomal single gene disorder and X-link disorders. - Human chromosomes always come in 23 pairs, i. e. 22 autosomes and pair of sex chromosomes. - Autosomal gene disorder happens in genes that can be found within the 22 pairs of non-sex chromosomes while X-linked disorder originated from the genes of sex chromosomes.

Chromosomal Disorders Chromosomal disorders may happen under certain conditions. It might be an excess or deficiency of the whole chromosome, Chromosomal rearrangement, and contiguous-gene syndrome. There are many structural abnormalities in the chromosomes and some of it are related to cardiovascular diseases that lead to congenital heart disease. Chromosomal rearrangement happens if there is breakage and reconstruction but in abnormal form. Structural rearrangement, however, may lead to loss or gain of genetic material but typically gaining human chromosomes is less harmful than the loss of genetic materials.

Down Syndrome

Turner Syndrome

Klinefelter Syndrome

Edward’s Syndrome

Patau Syndrome

Multifactorial Inheritance Multifactorial inheritance is not caused by some changes or abnormalities in a single gene or chromosome. It is basically caused by the combination of genetic changes that produces the disease. Multifactorial inheritance might happen 5 -10% in the first degree relatives with higher risk than that of the 2 nd degree relatives.

Gene Therapy Gene therapy is a method of treating or preventing diseases by replacing, or turning on or off genes of a patient’s cells. The process in gene therapy includes the use of vectors and non-viral method to move a DNA or genes to one cell or another. The two main types of Gene Therapy: 1. Somatic gene therapy is those which are not related to reproductive gene therapy. It is basically the introduction of genes to cell in target organ to produce enzyme which are needed by the body to function well. 2. Reproductive gene therapy or germ-line cell therapy is basically the introduction of corrective genes to sperm cells, egg cells, or even zygotes (4 day old). The main goal of this objective is to eliminate the abnormalities that can possibly be transmitted to the offspring. It is the alteration of genetic makeup of the offspring by targeting the abnormal genes in the parent’s sex cell.

Benefits and Disadvantages of Gene Theory Though gene therapy is not yet mastered, we believe that it is just only a matter of time. However, it provides us today these benefits: 1. It offers cure to several diseases like cancer, Parkinson’s disease, AIDS, asthma, diabetes, heart diseases as well as heredity diseases. 2. It can replace defective cells. 3. It has a promising potential not only in the field of medicine but in some related fields like agriculture. These are the disadvantages of gene therapy: 1. Modifying organisms means modifying its capabilities 2. Viral vectors could recover its ability to cause disease 3. It can damage the gene pool resulting to multigene disorder 4. High cost 5. Ethical issues