Overview of Chromosomal Disorders
Any kind of damage, mutation or irregularity in the number or structure of chromosomes is known as a chromosomal disorder. It is a vast term and can include a variety of abnormalities and changes in the chromosome as compared to its normal arrangement and structure. Chromosomal abnormalities are crucial and have serious health implications because chromosomes harbor genes; the genetic code of life. There are two types of chromosome in the body, somatic (known as autosome) and sex chromosome. In humans, there are total 46 chromosomes (23 pairs) and each chromosome harbors 100-1000 genes. There are 44 autosomes and 2 sex chromosomes (X and Y, male XY and female XX) in normal human beings.
There are major types of chromosomal disorders. They are:
- Structural abnormalities
- Numerical abnormalities
Causes and Risk Factors of Chromosomal Disorders
Structural abnormalities affect the structure or chromosome. This occurs due to insertion, deletion, translocation or duplication of a chromosomal part. Each type of abnormality has its own distinct affect and can lead to various disorder. Some of the common chromosomal disorders that occur due to structural changes in chromosome include Cri du chat (Cat Cry syndrome), Pallister Killian syndrome. Numerical abnormality occurs when there is presence or absence of complete chromosome, that include either one or more extra chromosome is present or there is any chromosome missing. The absence of one chromosome is called monosomy, presence of one extra chromosome is termed as trisomy, and presence of two extra chromosomes is called tetrasomy. The numerical abnormalities lead to various syndromes including Turner syndrome, Klinefelter syndrome, Down’s syndrome and Triple X syndrome. Mutations in genes can lead various lethal and non-lethal abnormalities, as the protein encoded by the gene becomes abnormal or truncated. Genetic mutations lead to hundreds of thousands of diseases, some of which include muscular dystrophy, Noonan syndrome, cystic fibrosis, cancer and sickle cells anemia.
Signs and Symptoms of Chromosomal Disorders
Most chromosomal abnormalities are fetal and lead to abortion of fetus, while milder abnormalities lead to mental disorders, heart problems, seizures, cleft palate or short stature.