Types of Genetic Disorders
A genetic disease is any disease caused by an abnormality in an individual’s DNA or genome. There are different types of genetic disorders that range from small mutation in a single gene to the addition or subtraction of an entire set of chromosomes. Genetic disorders are passed on from parents. However, genetic disorder can also occur when a mutation in a gene happens due to environmental exposure.
The following are the four types of genetic disorder:
Chromosomal abnormalities are genetic defects that are mainly caused by an error in the number or structure of chromosomes. Chromosomes are the tiny, string-like structures inside the body cells that carry the genes of an individual. When parents carry an abnormal chromosome, they are most likely to bear a child with mental or physical birth defects.
The following are the different types of chromosomal abnormalities:
1. Aneuploidy – this happens when chromosomes exceed or fall behind the normal number of chromosomes. Normally, humans have 23 pairs of chromosomes. Babies who are born with parents that have Aneuploidy can possibly develop Down syndrome and Turner syndrome.
2. Deletion – this happens when a part of a chromosome is missing
3. Inversion – this happens when a chromosome breaks and the piece turns upside down. Depending on the reattachment process, this inverted chromosome may cause a genetic defect
4. Translocation – this happens when an error occurs as chromosomes rearrange themselves
Single Gene Defects
Single gene defects occur when one single gene mutates. There are over 4, 000 diseases caused by single gene defect, which can be passed on by parents through genomic imprinting and uniparental disomy.
The following are three types of single gene defect:
1. Dominant – a type of defect wherein only one parent has an abnormal gene. However, babies born from parents with dominant single gene defect is 50 % at risk for developing diseases like Achondroplasia and Marfan syndrome.
2. Recessive – this occurs when two parents have abnormal genes. If both parents are carriers, their babies have 25 % chance of developing disorders like cystic fibrosis, sickle cell disease, or Tay Sachs disease.
3. X-linked – occurs when an error happens in the X chromosome. When a man carries the gene, his daughter has 1 or 2 chances of inheriting the defect. When a woman carries the gene, her son has 1 or 2 chances of inheriting the defect. The genetic disorders that are associated with the X-linked include Duchenne’s muscular dystrophy and Hemophilia.
Multifactorial problems are gene defects that do not follow a single gene or chromosomal abnormality patterns. They typically occur due to environmental factors, such as exposure to radiation and harmful chemicals. The inheritance of the defects caused by multifactorial problems is hard to predict. However, babies who are born with multifactorial problems usually have heart diseases, neural tube defects, brain defects, or cleft lip and cleft palate.
Teratogenic problems are defects that are caused by teratogens. These are substances that are known to cause abnormalities during the first trimester of pregnancy. Examples of these include alcohol, antibiotics, drugs, and lead.