Some Genetic Disorders are Inherited
There is a lot of discussion in the news about genetics and genetic studies. The ability to map the gene sequence during the Human Genome Project has led to amazing information about various health issues and heredity.
The information that has come to light so far is just the tip of the iceberg as medical researchers continue to explore the complexity of genes and gene mutations.
In the following sections, I will review some basic principles of genes before getting into a discussion of the role they play in disorders such as autism.
Thanks to the developing study of genes, the future holds much promise for those inheriting genetic disorders in terms of diagnosis and treatment. What are still mysteries today are quickly being unraveled and medical issues such as Autism Spectrum Disorders will hopefully become less puzzling as time progresses.
Getting Down to Gene Basics
You hear people using the terms DNA, chromosomes and genes, but if you asked them exactly what these terms mean they would probably have to dig out their high school biology books.
These topics don’t crop up in most everyday conversations, and yet for millions of children and adults with genetic disorders these are the words that get to the very core of their medical problems.
Living organisms are composed of cells and within each cell is DNA. DNA is the acronym for deoxyribonucleic acid. When you look at a picture of DNA what you see looks similar to a ladder that has been twisted several times. The wrapped DNA structures are called chromosomes.
If you think back to those high school biology lessons, you will remember there are 23 pairs of chromosomes in a normal cell. Genes are a segment of DNA and each gene determines a human’s characteristics.
Your genes determine the color of your hair, how tall you grow, your skin color and all your other characteristics that make you the person you are. But as it turns out your genes also play an important role in determining your propensity to put on weight or to develop certain diseases.
Each person has somewhere between 25,000 and 35,000 genes and when any of the them go awry, there are consequences. It is amazing that more people are not born with genetic defects because genes pass from human to human during conception.
The possibility of things going wrong are staggering and yet most people are born without serious medical issues or serious gene abnormalities.
Genes are like blueprints that get amended when the chromosomes from the sperm and egg unite at the moment of conception and a new structure or blueprint is created. This new structure determines the appearance and health of the human being formed.
Children With Autism
The prevalence of children with autism continues to climb. Teaching children with autism symptoms remains a major challenge for many schools. A recent report by the CDC (Center for Disease Control) reviewed information from 14 states and found that approximately 1 in – 150 children, 8 years of age have Autism Spectrum Disorder.
There is no national or Military registry so true prevalence is unknown but it is more common than childhood cancer, juvenile diabetes and pediatric AIDS combined. Although autism has not been proven to be a Genetic Disorder, potential genetic causes of autism studies continue.
What is a Genetic Disorder?
Sometimes genes variants exist in the sperm or egg cells and the new structure that is created contains the variant. In addition, aging and exposure to various chemicals and pollutants can cause cells to reproduce with gene mutations. In effect, that is a very simplified description of cancer – reproducing gene mutations.
It should be pointed out that carrying a gene mutation does not mean you are assured of developing a particular disease. There are many factors that come into play including gene dominance, environmental exposures and even diet. Scientists believe that most humans carry up to 20 disease genes and you could develop one, twenty or none of the diseases in your genetic coding.
Genetic disorders can take many forms. They include diseases such as Down Syndrome, Cystic Fibrosis, Sickle Cell Disease and Alzheimer’s Disease. Recently medical researchers have come to suspect that Autism Spectrum Disorders (ASD) are the result of abnormal genes that lead to problems in brain development.
This was first suspected when it was determined that parents with a child who has ASD have a higher risk of having another child with a similar disorder even if no one else in past generations had been autistic or had learning disabilities.
Genotype and Phenotype
When studying genes and inherited traits, there are two other important terms to understand. A genotype refers to a person’s exact genetic makeup. Your genotype refers to your particular set of genes without regard to how they behave, develop or change.
A phenotype, on the other hand, refers to how your genes develop or behave. It defines the physical properties of the genes which includes how they are transmitted and how they reproduce. Medical studies are beginning to focus on phenotypes and how they are related to the development of autism.
One of the complications researchers have experienced while trying to pinpoint the causes of ASD is the fact that the phenotypes and the etiology of the disorders are heterogeneous. There are never identical expressions of the disorder making it much more difficult to narrow the cause of the disorder.
One of the breakthrough studies in this field led to the identification of the Fragile X Syndrome. In the studies, it was determined that Fragile X Syndrome can lead to a child developing Autism even though this did not always happen. But doctors are using this relationship as a springboard into further research devoted to finding the “autism gene”.
Fragile X Syndrome results from the mutation of a single gene that is then passed from one generation to another. The gene is unable to produce the right amount of cell protein, especially in the brain cells, leading to improper cell functioning. The effects of this mutated gene reproduction ranges from a child having learning disabilities to severe mental retardation.
Genetic Testing…Perhaps Soon
There is no specific genetic test developed to diagnose autism or any ASD condition. Unfortunately the specific brain development abnormalities leading to autism or ASD conditions have not been identified yet.
But a child can be tested for the genetic disorder Fragile X which can assist with the diagnosis of ASD. Fragile X Syndrome genetic testing looks for the mutated gene causing the syndrome.
Another related genetic disorder is Turner Syndrome. It has been discovered that Turner Syndrome shares a phenotype with autism. The common phenotype is that people with autism and people with Turner Syndrome are unable to identify fear facial expressions on the faces of other people.
Turner Syndrome is the result of girls being born with only a single or partial X chromosome instead of two X chromosomes. Like with ASD, there is no single set of symptoms because the full impact of the syndrome is dependent on the cells affected by the X chromosome.
Generally the symptoms of Turner Syndrome include short height and lack of sexual development. The child may have learning disabilities, bone development problems, and drooping eyelids to name a few of the common physical problems.
It is becoming clearer through medical studies there is a link between genetics and ASD. As mentioned, the heterogeneous quality of the genetic material in people with autism makes it difficult to identify chromosomal changes that lead to the disorders. But some studies have begun to document some overlapping chromosomal change areas in people with autism
The only genetic testing done today is mostly related to Fragile X Syndrome, Turner Syndrome or a search for a chromosome abnormality.
Perhaps one day there will be a genetic test for autism, or an autistic disorder, though some researchers already are tending to believe autism is the result of a combination of inherited genes and gene mutation due to environmental exposures.
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