Research this topic using a minimum of 4 references, all of which must have been published within the last year. Third, write a 5-6 page double-spaced paper in which you do the following things: * describe the general topic you have selected * explain why this is an interesting and important area of biology, and it potential impact on medicine, agriculture, economics, criminal justice, or society. ` Human genetic diseases are a group of conditions that develops due to an abnormality in the individual’s genetic material known as ‘genome’ (Medline Plus. 2007).
This abnormality may develop due to formation of a different type of gene (variation), a modification of a gene (mutation), or addition or subtraction of a single or the full set of the chromosomes. There are four types of genetic disorders, namely, single-gene disorders, chromosomal abnormalities, Multifactorial disorders, and mitochondrial disorders (University of Utah. 2007). Single-gene disorders (or Mendelian disorders) are a type of genetic disorders that develops due to alterations in the DNA sequence of a particular gene (the DNA sequences are present inside the gene).
A gene contains several proteins that express certain characteristics and enable important activities in the cells and the tissues. It is associated with a single genetic locus (location of the gene) present on the chromosomes. The effect the defective gene produces (symptoms and signs) are known as ‘phenotype’. These may be of two types, namely, homozygous conditions (in which both the copies are similar) and heterozygous (in which both the copies of the genes are not similar) (Neal Sondheimer. 2007).
A mutation in the gene leads to disturbances in carrying out the normal functions of the body. Some of the single-gene disorders include Sickle cell disease, phenylketonuria, neurofibromatosis, Marfan’s syndrome, Huntington’s disease, cystic fibrosis, etc, disorders (University of Utah. 2007). It affects one in every 200 children born, and actually more than 6000 single gene diseases exist (Neal Sondheimer. 2007). These single-gene disorders can be transmitted to the offspring in 3 different patterns, namely, autosomal-dominant, autosomal-recessive and sex-linked.
In autosomal dominant disorders, only one copy of the defective gene needs to be inherited from either of the parent for the child to develop the disorder (Neal Sondheimer. 2007). In an autosomal recessive disorder, both the copies of the defective gene need to be inherited from both the parents for the child to develop the disorder. If the child inherited only one pair of the disorder, it can be a carrier of the disease (transmit the defective gene to the next generation), and usually does not suffer from the disorder. However, some individuals may suffer from a milder version of the disorder (Neal Sondheimer.
2007). Sex-linked disorders are a group of genetic disorders that is transmitted through the X- or the Y- chromosomes (sex-chromosome, namely the 23rd pair). Some of the X-linked disorders include Duchenne muscular dystrophy and Hemophilia A (Neal Sondheimer. 2007). On the other hand, autosomal disorders are transmitted through the non-sex chromosomes (namely pairs one to 22). Sex-linked disorders may be dominant (one of abnormal gene is to be inherited from the parents to develop the disease) or recessive (both the abnormal genes needs to be inherited from both the parents to develop the disease) (Brian Kirmse.2006).
Multifactorial disorders are a group of genetic disorders that develop due to interplay between the genetic factors (usually a mutation) and the environmental factors (University of Utah. 2007). The genes that can lead to the development of several diseases are present on the chromosome, and when certain environmental factors are present, the disease may develop. Some of the common Multifactorial disorders include hypertension, arthritis, Alzheimer’s disease, obesity, stroke, coronary heart diseases, neoplasm, diabetes, hypothyroidism, etc (University of Utah.2007).
Chromosomal disorders are conditions that arise due to abnormality with the long-thread-like structures present in the nucleus that carry the genes. In the human body, 46 chromosomes (or 23 pairs) are present, out of which 22 pairs are of the non-sex or autosomal variety and the single pair is of the sex variety. This single pair is XX in females and XY in males (Neal Sondheimer. 2007). The may be an increase or a decrease in the number of genes present of a particular chromosome. Besides, a portion or the entire chromosome may become abnormal.
A portion of a chromosome may be detached and may swap places with portions of another chromosome (such as in Philadelphia chromosome in which the chances of developing certain leukemia are very high) (Neal Sondheimer. 2007). Chromosomal abnormalities can be classified into two types, namely, numerical abnormalities (in which the number of chromosomes is altered) and structural abnormalities (in which a portion of the chromosome is deleted, duplicated, translocated or inversed) (NHGRI. 2007). Chromosome disorders can usually be detected by studying the cells under a microscope.
Some of the other chromosomal disorders include Down’s syndrome, Cr-du-Chat syndrome, Klinefelter syndrome, Turner’s syndrome, William’s syndrome, etc (University of Utah. 2007). The mitochondria are minute structures present within the cytoplasm of the cell that brings about cell respiration; utilize several chemicals to produce energy (in the form of ATP) for the functions of the cell. The mitochondria contain DNA which is unique in a way that it is not present on the chromosomes. An abnormity with this DNA can result in a disorder that can be inherited.
The mitochondria are inherited from the mother, and hence, if the mother is suffering from a disorder of the mitochondrial-DNA, she may pass it own to her child. About 5 to 50 pieces of DNA in the form of a circle are present in each mitochondrion. Disorders in the mitochondrial-DNA can bring about abnormalities in the metabolism, growth and development, sight, hearing, heart function, etc (Neal Sondheimer. 2007). Human genetic diseases have caused a lot of problems to several individuals who suffer from the disease. The scientific community has developed several techniques to sort out this problem.
Amongst the several techniques available to treat genetic diseases are genetic testing and gene therapy. Gene therapy is a technique in which an abnormal gene is altered so that the expression of the gene is corrected and the disorders can be treated. Several techniques are utilized to correct genetic disorders such as introduction of a gene into the genome, translocation of the abnormal gene with a normal gene, restoring the defective gene through a process of reverse mutation, controlling the expression of the defective gene (HGP.
2005), introduction of DNA to help normal cells to fight the diseased cells or introduction of a DNA into the diseased cells so that they are destroyed (NCI. 2006). Gene therapy is still in its infancy stages and several clinical trails are being conducted. A virus can be utilized to position the DNA into the gene (NCI. 2006). The viruses have developed means of entering the cells and positioning their genetic material into the genes in such as way that disease is caused. Some of the viruses that are utilized in gene therapy include retrovirus, adenovirus, adeno-associated virus, pox virus, herpes virus, etc (NCI.2006).
They may modify the host’s DNA temporarily or permanently. The viruses may be modified in such a way that they do not cause disease, identify the cells in a better way and they specifically enter certain genes and cause alterations. Another method which can be utilized to treat genetic diseases is to introduce the DNA into certain cells (which can enter the cell and bring about changes) (HGP. 2005). The DNA can also be delivered using an aqueous core surrounded by an artificial lipid sphere. This can enter the plasma membrane of the cell and alter the abnormal DNA present in the gene (HGP.2005).
One of the first diseases to be treated by gene therapy was ADA deficiency, in which the individual developed insufficiency of the ADA enzyme resulting in defective functioning of the immune system. Such individuals are at a high risk of developing severe infections (which can also be life-threatening). The disease is now being treated by introducing normal DNA into the gene, which will alter the genetic material and lead to the production of the enzyme ADA, thus helping to correct the deficiency and reducing the symptoms (NCI. 2006).
Genetic testing is a procedure in which the genetic material is tested by observing them so that several genetic disorders can be identified and treated appropriately. Biochemical tests can also be performed to study the chromosomes. Gene testing may be utilized in several disorders such as to screen the individual for carrier status, screening the embryo or fetus (prenatal diagnosis), determining the future progression of a genetic disorder, establishing the diagnosis, forensic tests, etc (HGP, 2006). The gene test is usually performed on a sample of the individual’s blood or tissues.
In certain genetic tests, probes are utilized which bind to specific complementary bases in the DNA and help to identify the presence of a particular genetic material. If a gene is suspected to be abnormal, it is usually compared to the normal version of the gene through specialized examination procedures (HGP, 2006). Genetic testing helps to study and detect the presence of several genetic disorders. On the other hand, an individual’s genetic material can be studied through gene testing, and the conditions to which he/she is susceptible can be determined.
Individuals who are at a high-risk of developing several disorders can be monitored through genetic testing. As genetic testing is still in its infancy stages, problems in interpretation of the results, laboratory errors, ethical issues, potential misuse situations, etc, may occur (HGP, 2006).
References: Human Genome Project. “Gene Testing. ” 2006. HGP Information. 16 Apr 2007 http://www. ornl. gov/sci/techresources/Human_Genome/medicine/genetest. shtml Human Genome Project. “Gene Therapy. ” 2005. HGP Information. 16 Apr 2007 http://www. ornl. gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml National Cancer Institute. “Gene Therapy for Cancer: Questions and Answers. ” 2006. NCI. 16 Apr 2007 http://www. cancer. gov/cancertopics/factsheet/Therapy/gene Neal Sondheimer.
“Genetics. “ 2005. Medline Plus. 16 Apr 2007 http://www. nlm. nih. gov/medlineplus/ency/article/002048. htm NHGRI. “Chromosome Abnormalities. ” 2007. NIH. 16 Apr 2007 http://www. genome. gov/11508982 The University of Utah. “What are Genetic Disorders? ” 2007. Genetic Science Learning Center. 16 Apr 2007 http://learn. genetics. utah. edu/units/disorders/whataregd/.