What are Genetic Disorders?
Genetic disorders can also cause rare diseases. This group of cases affects less than 200,000 people in the U.S. According to experts, there may be as many as 7,000 cases. Genes are the basic functional unit of heredity. Genes are composed of DNA that holds the genetic information to instruct the cells to translate different proteins and other hereditary components. DNA or many times RNA is the genetic material in almost all living organisms. RNA is more unstable than DNA which is why DNA is the genetic component in all organisms except some. Sometimes, under some faulty conditions, the genes undergo mutation causing to falter the genetic code. Faulty genes produce faulty proteins that do not work properly. This leads to malfunctioning and genetic disorders.
Some of these genetic disorders are present by birth and some are acquired due to mutations in genes. Hence, genetic disorders are categorized into two categories:
Mendelian disorders which are acquired due to mutation in the genes.
Chromosomal disorders which are from the mutation in the chromosome.
Common Genetic Problems Include:
AA amyloidosis.
Adrenoleukodystrophy (ALD).
Ehlers-Danlos syndrome.
Mitochondrial Diseases.
Usher syndrome.
We will explore more about genetic disorders in this chapter.
Types of Genetic Disorders
1. Mendelian Disorder
Mendelian disorders are either autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive, or mitochondrial and occur due to mutations in a single gene. These disorders can be detected by pedigree analysis. The genetic locus at which the mutation takes place may be a sex chromosome or an autosome and it may be in a recessive or a dominant mode. An autosomal recessive disease is articulated when the mutant gene is present in the homozygous state. In such cases, both the parents are heterozygous, carrying one copy of the mutant gene and one copy of a normal functional gene. In autosomal traits, females and males are equally expected to be affected. Other types of Mendelian disorders are Autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked chromosomal, and mitochondrial.
Examples of Mendelian Disorders are:
Autosomal Recessive Disorder - Cystic Fibrosis.
Sex - Linked Disorder- Hemophilia.
Autosomal Recessive Disorder - Albinism and Sickle Cell Anemia.
2. Chromosomal Disorders
Genetic disorders arising due to mutation in the chromosome are chromosomal disorders. Alteration in the number and functioning of the chromosomes leads to chromosomal disorders. A chromosomal disorder affects many genes at a time and can be fatal. It may occur due to the loss or gain of a whole chromosome.
Examples of Chromosomal Disorders are as Follows:
Down’s Syndrome which occurs due to the addition of a chromosome on chromosome 21.
Turner’s syndrome is marked by the absence of an X chromosome.
Kleinfelter’s syndrome is marked by the addition of an X chromosome, and so on.
3. Multifactorial Genetic Inheritance
Multifactorial inheritance also refers to polygenic inheritance. When many factors occur at the same time leading to genetic anomalies, it is known as multifactorial genetic inheritance. In such cases, environmental factors take place along with gene mutation.
Examples of Multifactorial Diseases are as Follows:
Heart Disease
High Blood Pressure
Alzheimer’s Disease
Obesity
Diabetes
Cancer
Arthritis
4. Mitochondrial Inheritance
These kinds of genetic disorders arise as a result of mutations in the non-nuclear mitochondrial DNA. Generally, in such cases, each mitochondrion has 5 to 10 pieces of DNA. These anomalies are inherited from the mother.
Examples of Such Diseases are:
Leber’s Hereditary Optic Atrophy (LHON).
Myoclonic epilepsy with ragged red fibers.
Mitochondrial encephalopathy.
Lactic acidosis.
List of Some Genetic Disorders
Cystic Fibrosis
Thalassemia
Huntington’s Disease
Hemochromatosis
Turner’s Syndrome
Klinefelter's Syndrome
Leber’s Hereditary Optic Atrophy
Cancer
High Blood Pressure
Obesity
Albinism
Apert Syndrome
Down’s Syndrome
Genetic Counselling
Genetic counseling is the process of communication to help individuals or families understand and adapt to the medical implications of genetic disorders. It is the way of detecting if the child before birth will have a genetic disease or can develop any genetic disorder. Counselors in this field can help individuals and their families cope with the effects of a genetic disorder and treat them in some ways.
A few genetic disorders are treated by gene therapy. Research is still underway to know more about genetic diseases and how to treat them. Medical science professionals are trying their best to deal better with such anomalies.
What are the Symptoms of Genetic Disorders?
Symptoms vary depending on the type of disease, affected organs and severity. You may have:
Behavioural changes or distractions.
Respiratory problems.
Mental deficiency, in which the brain is unable to process information as it should.
Developmental delays involving speech or community skills challenges.
Eating and digestive problems, such as difficulty swallowing or not being able to process nutrients.
Orthopaedic organs or face, including missing fingers or lips and a broken lip.
Movement disorders due to muscle stiffness or weakness.
Neurological disorders such as fainting or stroke.
Poor growth or short stature.
Sight or loss of hearing.
What is the Treatment for Genetic Disorders?
Many genetic disorders have no cure. Some have over-the-counter medications that may slow down the progression of the disease or reduce its effect on your health. The type of treatment that is best for you depends on the type and severity of the disease. With others, we may not get treatment but we can provide health monitoring to try to catch problems early.
You may need:
Symptomatic medications or chemotherapy to slow the abnormal cell growth.
Nutrition advice or dietary supplements to help you get the nutrients your body needs.
Physical, occupational or speech therapy to improve your skills.
Blood transfusions restore healthy blood cell levels.
Surgery to repair unusual structures or treat problems.
Special treatment, such as radiation therapy.
An organ transplant, a procedure to replace a deformed limb from a healthy donor.
What are the Methods of Identification of Genetic Problems?
If there is a family history, DNA testing of genetic disorders can be an important part of starting a family. Options include:
Carrier Testing: This blood test shows that you or your partner are experiencing genetic mutations. This is recommended for anyone considering pregnancy, even if you do not have a family history.
Prenatal Screening: This test usually involves a blood test for a pregnant woman that tells the person how much the fetus is likely to have a normal chromosome.
Prenatal Diagnostic Tests: You can find out if your unborn baby is at high risk for certain genetic problems. Prenatal testing uses a sample of uterine fluid (amniocentesis).
Newborn Test: This test uses a sample of your newborn’s blood and is performed on all babies born in Ohio. Early detection of genetic disorders in life can help your child to receive timely care if needed.
FAQs on Genetic Disorders
1. What are genetic disorders and how do they occur in humans?
Genetic disorders are health conditions caused by changes or mutations in DNA or genes. These mutations can be inherited from parents or occur spontaneously. Faulty genes or altered chromosomes lead to improper production of proteins, resulting in various symptoms or developmental issues.
2. How are genetic disorders classified according to the CBSE Class 12 syllabus?
Genetic disorders are primarily classified into the following types:
- Mendelian (Single-Gene) Disorders: Caused by mutations in a single gene, showing clear inheritance patterns (autosomal dominant/recessive, sex-linked, or mitochondrial).
- Chromosomal Disorders: Result from structural or numerical abnormalities in chromosomes, such as Down’s Syndrome or Turner’s Syndrome.
- Multifactorial Disorders: Involve multiple genes and environmental factors, e.g., diabetes or heart disease.
- Mitochondrial Disorders: Caused by mutations in mitochondrial DNA, inherited maternally.
3. What are the most common examples of Mendelian and chromosomal genetic disorders?
Some common Mendelian disorders include Sickle Cell Anaemia, Cystic Fibrosis, Thalassemia, and Hemophilia. Chromosomal disorders examples are Down’s Syndrome (trisomy 21), Klinefelter’s Syndrome (XXY), and Turner’s Syndrome (monosomy X).
4. How does genetic counseling help families manage genetic disorders?
Genetic counseling provides individuals and families with expert guidance to understand risks, inheritance patterns, and health implications of genetic disorders. It assists in medical decision-making, offers support on prenatal testing, and helps families take preventive actions or early interventions.
5. What are the key methods used for diagnosing genetic disorders?
Diagnosis is achieved by:
- DNA testing to detect gene mutations.
- Karyotyping for chromosomal abnormalities.
- Carrier and prenatal screening to assess inherited risks.
- Newborn screening for early detection and timely care.
6. Explain the difference between autosomal dominant and autosomal recessive disorders.
In autosomal dominant disorders, a single copy of the mutated gene (from either parent) is sufficient to cause the disease. In contrast, autosomal recessive disorders require both gene copies (one from each parent) to be mutated for the condition to manifest in the offspring.
7. What are the major symptoms observed in children born with genetic disorders?
Children may show:
- Developmental delays (speech, cognitive skills)
- Physical abnormalities (facial features, missing digits)
- Neuromuscular issues (muscle weakness, movement difficulties)
- Metabolic or digestive problems
- Poor growth or short stature
8. Why do chromosomal disorders often cause more severe symptoms than single-gene disorders?
Chromosomal disorders affect multiple genes at once due to large changes in chromosome number or structure, leading to widespread disruption in cellular functions. This results in more complex and severe clinical outcomes compared to single-gene (Mendelian) disorders which only impact specific proteins.
9. How do environmental factors influence the risk of developing multifactorial genetic disorders?
Environmental factors such as diet, radiation, chemical exposure, smoking, or lifestyle can interact with inherited gene mutations to increase susceptibility to multifactorial disorders like diabetes, hypertension, or cancer. These disorders arise when genetic predisposition combines with environmental triggers.
10. What preventive strategies can reduce the incidence or impact of genetic disorders in a population?
Preventive steps include:
- Genetic screening and counseling before planning a family
- Prenatal and newborn testing for early detection
- Avoiding known mutagens (radiation, harmful chemicals)
- Education about inheritance risks and carrier status
- Timely medical interventions and health monitoring
11. How does mitochondrial inheritance differ from nuclear gene inheritance in genetic disorders?
Mitochondrial inheritance involves genes present in the mitochondrial DNA, which is inherited exclusively from the mother. Unlike nuclear gene disorders, both males and females can be affected, but only females can pass the disorder to their children.
12. What misconceptions do students often have about the inheritance of genetic disorders?
Common misconceptions include:
- Believing only one parent needs to be a carrier for all types of inherited disorders
- Assuming chromosomal disorders are always inherited rather than arising from random events
- Thinking all genetic disorders are fatal or untreatable
- Misunderstanding patterns of dominant, recessive, and X-linked inheritance
13. Can lifestyle interventions help manage genetic disorders, and if so, how?
Yes, while genetic disorders cannot be cured, lifestyle modifications such as balanced nutrition, exercise, and regular medical monitoring can help manage symptoms and improve quality of life. For some metabolic or multifactorial genetic conditions, these interventions can delay progression and reduce complications.
14. Why is pedigree analysis important in the study and diagnosis of genetic disorders?
Pedigree analysis helps trace inheritance patterns of diseases within families, distinguishing between autosomal and sex-linked traits. It is valuable for recognizing carriers, predicting risks for offspring, and making informed medical or reproductive decisions.
15. How can awareness of genetic disorders promote better health outcomes in society?
Increasing awareness leads to early screening, accurate diagnosis, and timely intervention. It helps reduce stigma, supports research, and encourages families to seek expert counseling, ultimately improving health outcomes by minimizing severity and transmission of genetic disorders.
