In This Article
In This Article
The human genome is complex, as identified by the Human Genome Project. It contains instructions on a person’s growth and development. The human genome, however, is subject to changes. These changes can affect molecules that make up the DNA or even chromosomes.
Genetic disorders are diseases that are caused by gene mutations, or changes, in a person’s normal DNA sequence. The DNA mutations may be caused by errors in DNA replication or environmental factors. Examples of environmental factors are radiation exposure and cigarette smoking.
The DNA contains genetic material. It supplies the code for making proteins that allow the body to perform its functions. When a part of the DNA is changed, protein-coding is affected. As a result, the body isn’t able to function as it should.
The impact of DNA changes depends on where the mutations occurred. Some mutations will have little to no effect. Others will have such a profound effect that they will alter the body’s cell biology. This will cause a genetic disorder.
Genetic disorders are grouped into three main categories. They are determined by the cause or location of the defect.
Single gene disorders are called such because the defects are in one particular gene. Most of the time, inheritance patterns are simple and predictable. These disorders are further classified into three types:
Chromosome disorders are also called chromosomal abnormalities. They are genetic diseases that result from changes in the structure or number of chromosomes. Down’s syndrome, or Down syndrome, is a chromosome disorder.
These are also known as complex disorders or multifactorial inheritance. Multifactorial disorders are caused by changes that occur in multiple genes. Often, these are a result of a complex interaction between lifestyle and environmental factors. Cancer is a multifactorial disorder.
A genetic diagnosis is based on several approaches. They are as follows:
During a physical examination, a geneticist will conduct a thorough exam. It may involve measuring distances between eyes, length of limbs, and head circumference. This is because some genetic disorders have distinct physical characteristics associated with them. Sometimes, facial features can suggest the presence of a genetic condition.
Additionally, eye exams and neurological exams are also performed. Imaging studies such as magnetic resonance imaging (MRI), computerized tomography (CT) scans, and x-rays may be used to get a picture of the structures found inside the body.
A person’s medical history provides valuable insights into a person’s overall health and well-being. This requires a meticulous history-taking process, with information going back as far as birth.
It is important to include past (and present) health issues, medications, and allergies. Information on past surgeries and hospitalizations is also needed. If the individual has undergone genetic testing, the results should be divulged.
Genetic conditions are often passed down from generation to generation. Information regarding the state of health of family members is very important. This is an essential tool in diagnosing conditions caused by mutations in the DNA.
Parents, siblings, children, and other relatives will be asked about their health conditions. This is usually done either by a genetic counselor or a doctor. Information obtained usually holds valuable clues. It may reveal the inheritance pattern of a certain genetic disorder that runs in the family.
Laboratory tests, such as genetic testing, are used to diagnose genetic disorders.
In the diagnosis of a genetic disorder, there are several types of genetic tests used. These include:
Cytogenetic tests are used to detect structural abnormalities in chromosomes. Biochemical testing tests for protein function. On the other hand, molecular testing detects abnormalities in DNA sequencing.
Many genetic conditions can now be tested using a screening test and genetic testing. For some conditions without a genetic test, it may be because the genetic cause of such a condition is yet unknown. Or, it may be because a test has not been developed yet.
In cases such as these, it may help to sequence the entire genome. This could help locate the genetic variant responsible for the condition.
A genetic disorder may be diagnosed during a person’s lifetime. From birth to old age, a diagnosis of a genetic disorder may be made. This is because some features of the genetic condition appear very early or too late. The availability of testing may also affect diagnosis.
A diagnosis is very important, even if there’s currently no treatment available. This can help manage expectations and identify advocacy resources and useful support.
There are more than 6,000 genetic disorders, and most of these are seriously debilitating. Some cause birth defects, and some are even fatal.
Below are some of the most common genetic disorders. It includes their mode of inheritance and the clinical features they present.