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The secret of chromosomal abnormalities: Why do some people have an extra chromosome 21?
In the microscopic world of life, chromosomes exhibit their unique and complex structure. However, when this structure becomes abnormal, it may cause a series of health problems. When there are missing, extra, or irregular parts of a chromosome, it is called a chromosomal abnormality. These abnormalities are usually manifested through numerical abnormalities (such as abnormalities in the number of chromosomes) or structural variations, thereby affecting the overall genetic information.
Chromosomal abnormalities often occur during cell division and can lead to a variety of health conditions, including Down syndrome and Turner syndrome.
Number exception
When an individual has an abnormal number of chromosomes, it is called aneuploidy. For example, when one pair of chromosomes is missing, it is called a monosomy; when there are extra copies of a chromosome, such as trisomy or tetrasomy, it is part of aneuploidy. Down syndrome is a well-known example because it is a developmental disorder caused by an extra copy of chromosome 21 (known as trisomy 21).
Structural abnormality
In addition to numerical abnormalities, structural abnormalities of chromosomes are also an important form of chromosomal abnormalities. This abnormality may appear in the form of deletions, duplications, inversions, insertions, translocations, and circular chromosomes. Taking deletion as an example, Wolf-Hirschhorn syndrome is a disease caused by the deletion of part of the short arm of chromosome 4. These structural changes may severely affect the normal function of genes, leading to various health problems.
Research has found that structural variations in chromosomes not only affect gene expression, but may also lead to the occurrence of certain cancers.
Hereditary and acquired chromosomal abnormalities
Most chromosomal abnormalities occur during the fusion of eggs or sperm, so they can be found in every cell of an individual. However, certain abnormalities may occur after fertilization, leading to what is known as "chimerism," in which some cells contain the abnormality while others do not. In some cases, chromosomal abnormalities can be inherited from a parent or arise entirely new (a "de novo" mutation).
Detection and diagnosis
There are currently many methods for detecting chromosomal abnormalities, and different techniques and samples can be selected based on the information required. For prenatal diagnosis of the fetus, amniocentesis or chorionic villus sampling is usually performed for analysis. In preimplantation diagnosis of embryos, a blastocyst biopsy is performed. These technologies can effectively identify possible chromosomal abnormalities, allowing for early intervention and treatment.
The impact of environmental factors
Research shows that certain environmental factors can increase a person's risk of developing chromosomal abnormalities. For example, when men are exposed to cigarettes, benzene, pesticides and certain chemicals, they may increase the chance of sperm aneuploidy, which is related to DNA damage. This means that lifestyle and environmental exposures undoubtedly have a significant impact on chromosomal health.
Whether it is genetic or environmental factors, the mechanism of chromosomal abnormalities reminds us of the importance of protecting our own health.
Final Thoughts
As research into chromosomal abnormalities becomes more intensive, scientists continue to explore how to prevent and treat these health problems. However, there are still many unknown areas waiting for us to uncover and explore. Are we prepared to face these challenges to advance genetic health and the future of humanity?
