Genetic Disorders: What are They, Types, and More

Genetic disorders are conditions that occur when there is a mutation in the DNA.

There are a number of genetic disorders.

Different cells within your body contain molecular DNA. Moreover, this molecule is able to provide the cells with instructions on how to function.

A change or mutation within the DNA can lead the cell to function abnormally.

This leads to genetic disorders.

However, it is important to note that carrying mutations does not always mean that you will end up with a disease.

Different types of genetic disorders are single-gene, multifactorial, and chromosomal disorders among others.

Keep on reading to learn more about genetic disorders, different types, the main symptoms of each type, and how they develop.

Genetic Disorders

Genetic disorders are conditions that occur as a result of changes or mutations to the DNA within the cells of the body.

A number of cells in your body contain long strands of DNA that provide the cells with instructions.

Each DNA strand is tightly coiled around a protein i.e. a histone.

This coiled structure is called a Chromosome.

Moreover, chromosomes contain small sections of DNA, i.e. genes.

These genes provide your body with specific instructions.

Each human cell normally contains 23 pairs of chromosomes, with one of each pair that comes from each parent.

Thus, you can say that every person has two copies of every gene.

In case there is a change or fault in the DNA, it can cause a genetic condition.

As genes pass from parents to their children, these disorders can be heritable.

However, not everyone with a genetic condition in their family will experience symptoms of genetic disorders.

Furthermore, genetic conditions can affect any gene or chromosome.

This means that there is a wide range of genetic disorders, each causing different symptoms.

Human Genome

A human genome refers to all the genes and DNA that are crucial to building and maintaining a human.

The Human Genome Project, HGP, project established the sequence of the human genome of different genes.

Moreover, the HGP estimates that there are about 20,000 to 25,000 genes in the human genome.

The DNA inside these genes contains four chemical bases that act as units of information.

These are:

• adenine
• cytosine
• guanine
• thymine

Each DNA molecule contains two twisted strands of DNA.

Pairs of chemical bases connect one DNA strand to the other and resemble rungs of a ladder.

Furthermore, the base pairs of chemicals between each strand always combine in a certain way.

For instance, adenine on one DNA strand will always pair with thymine on the opposite DNA strand.

Additionally, the order of the chemical base pairs in each molecule of DNA affects what instructions that DNA will provide to the body.

DBNA sequencing involves reading the order of these base pairs.

Development of Genetic Disorders

It is important to note that genetic conditions tend to run in families.

Parents tend to pass genes on to their children and some of these genes can contain the basis of a genetic disorder.

However, each parent only passes down half of their genes.

The version of each gene that a parent will pass down is an Allele.

In case two alleles from each parent differ, the body may only take instructions from one of them.

Moreover, the allele that the cells will take instructions from is the Dominant Allele,

While the other one is the Recessive Allele.

Some genetic conditions are carried by the dominant allele, while others are carried by a recessive allele.

In general cases, a person will only inherit a certain genetic disorder if they have at least one dominant allele for the disorder or two recessive alleles for the disorder.

Single Inheritance Genetic Disorders

A single inheritance or monogenic disorder is a condition that results from a fault or mutation within a single gene.

One of the important things to note is the dominant disease are single-gene disorders that occur in the heterozygous state.

This is when an individual has only one mutant copy of the relevant gene and one healthy gene.

The effects of the mutant version of the gene or allele will override the effects of the healthy one.

Thus, the mutant allele will cause disease symptoms even though a healthy allele is present.

Moreover, dominant disorders tend to crop up in every generation of the affected family.

This is because everyone carrying a dominant mutant allele will show the symptom of the disease.

Also, dominant disorders tend to spread vertically down the family trees, from parent to child.

However, in rare cases, when an individual has two copies of the mutant gene or is homozygous, the disorder symptoms will be more severe.

The following are certain examples of this type:

Huntington’s Disease

Huntington’s disease is a degenerative brain disorder.

It causes:

• uncontrolled movement
• emotional disturbances
• cognitive decline

Moreover, this disease tends to develop due to mutation on the dominant allele within chromosome 4.

People with this allele will gradually develop this condition.

Treatment 

There is no way to stop or slow the progression of this disease currently.

However, with the help of certain medications, doctors can help a person manage their symptoms.

These include medications to help control involuntary movements and medications to treat mood shifts, irritability, and depression.

Sickle Cells Diseases

SCDs, sickle cell diseases are a group of conditions that affects your red blood cells.

Sickle cell anemia is a type of SCD in which the red blood cells that transport oxygen to the tissues of the body are misshapen.

Their unusual shape means that they are less able to transport oxygen, and more likely to clump together.

Clumps of these blood cells can block the blood vessel, and potentially causes:

• pain
• infections
• acute chest syndrome
• stroke

Moreover, SCDs occur as a result of mutations in the HBB genome which provides instructions for the production of red blood cells.

Also, SCDs are recessive which means that you will need to inherit two alleles containing mutations in order to have this disorder.

Treatment

Treatment for SCDs helps to prevent complications and prolong life.

Your doctor may prescribe the medication hydroxyurea.

This will help to increase the size of red blood cells, thereby increasing the amount of oxygen each cell will transport.

Muscular Dystrophies

This is a group of genetic disorders that can cause muscle damage and weakness over time.

They occur due to mutation in the DMD gene.

Muscular dystrophies are X-linked disorders, which means that they affect a gene on the X chromosome.

Moreover, these conditions are more common in males than in females.

This is because males have one X chromosome and one Y chromosome, while females have two X chromosomes.

In females, the unaffected X chromosome can counteract the affected one, however, in males, there is no other X chromosome to do this.

Treatment 

Currently, there is no treatment to stop or reverse muscular dystrophies.

However, treatment aims to prevent complications and improve the quality of life.

Examples are:

• physical therapy that helps to maintain muscle strength and flexibility
• respiratory therapy that helps to maintain the strength of the respiratory muscle
• speech therapy in cases there is a weakness of the throat or facial muscle affects speech
• occupational therapy to help you use assistive devices like wheelchairs

It is important to note that one or more of the following medications can help to slow or control the symptoms:

Glucocorticosteroids help to increase muscle strength and slow the progression of muscle weakness

Immunosuppressants help to delay damage to muscle cells.

Anticonvulsants help to control muscle spasms and seizures.

Antibiotics to treat respiratory infections.

Multifactorial Inheritance Genetic Disorders

Multifactorial inheritance disorders, MIDs are conditions that develop due to a combination of genetic factors and environmental or lifestyle factors.

Some of these non-genetic factors are:

• smoking
• drinking alcohol
• eating an unhealthful diet
• not getting enough sleep
• living in an area that has high levels of air pollution

Moreover, some conditions that may fall into the category of MIDs are:

Asthma, heart disease, diabetes, certain cancers, schizophrenia, Alzheimer’s disease, and multiple sclerosis. 

Furthermore, certain genetic mutations can also increase the risk of these conditions.

However, there is no clear pattern of inheritance.

Chromosomal Abnormalities

These abnormalities are problems that affect a chromosome and can involve:

• having a missing chromosome
• having an extra chromosome
• a chromosome that has some kind of structural abnormality

Chromosomal abnormalities often occur when there is an error as a cell is dividing.

These errors often occur within the egg or sperm, however, can also happen after conception.

Moreover, it is possible to inherit a chromosomal abnormality from a parent.

However, some develop within a person for the first time.

Some examples of chromosomal abnormalities are:

Down Syndrome

Down Syndrome is a type of chromosomal abnormality that affects intellectual and physical development.

Moreover, it occurs when a person receives an extra copy of chromosome 21.

This means that each cell within the body will have three copies of chromosome 21 instead of two copies.

Treatment 

This is a lifelong condition, however, with the help of different types of therapies, it can help intellectual and physical development.

Examples are:

• occupational therapy
• physical therapy
• speech therapy
• receiving extra help or attention at school

Wolf-Hirschhorn Syndrome

Wolf-Hirschhorn syndrome is a chromosomal abnormality that tends to affect the entire body.

The major features of this condition are:

• delayed growth and development
• reduced muscle tone
• intellectual disabilities
• seizures

Moreover, this syndrome tends to develop due to a relation of a section of chromosome 4.

In most cases, it occurs for the first time within the person who has this disorder.

However, it is also possible for a person to inherit this condition from a parent who has a chromosomal abnormality.

Treatment 

There is no treatment for Wolf-Hirschhorn syndrome.

But the following treatment can help a person to manage their symptoms and improve their quality of life:

• physical or occupational therapy
• counseling
• drugs that can help with specific symptoms like seizures

Mitochondrial Inheritance Genetic Disorders

Mitochondria are biological structures that exist in the cells of the body.

These have the ability to generate most of the energy that the cells need to carry out their biochemical reactions.

Moreover, mitochondrial disorders are a group of genetic conditions that affect DNA within the mitochondria themselves.

These DNA mutations or changes result in the mitochondria failing to produce enough energy to sustain the cells of the body.

Furthermore, mitochondrial disorders tend to affect any organ or part of the body.

The symptoms a person will experience will depend on the part of the body the disorder affect.

Some possible symptoms of these disorders are:

• poor growth
• muscle weakness
• loss of muscle coordination
• visual problems
• hearing problems
• seizures
• developmental delays.

Some other symptoms are intellectual disabilities, autism spectrum disorder, diabetes, heart, liver, or kidney disease, and respiratory disorders.

Mutations in mitochondrial DNA are inherited materially which means a mother can pass down these disorders.

Treatment 

There is currently no cure or highly effective treatment for the mitochondrial disorder.

However, nutritional management, vitamin supplements, amino acid supplements, and medications to treat specific issues like muscle weakness or seizures can help manage the disorder.

Conclusion

Genetic disorders occur as a result of changes or mutations to the DNA and this can affect the whole chromosome or the specific gene within the chromosomes. DNA mutations can also occur within the DNA of mitochondria which power the cells of a person.

Most genetic conditions tend to be heritable, however, can also occur for the first time within a person who experiences a specific disorder.

Moreover, genetic disorders are lifelong conditions and treatment tends to focus on helping a person manage the symptoms, preventing complications, and improving quality of life.

However, in some cases, there may be medications available to help slow the progression of a particular disease.