What are chromosomal abnormalities?

Chromosomal abnormalities are defects in the structure or number of chromosomes. Depending on the nature of the abnormality, these abnormalities may be incompatible with life, in which case the baby will miscarry early in the pregnancy, or they may be almost unnoticeable, sometimes not becoming apparent until someone undergoes routine medical tests. something like an adult It is estimated that about one in 150 babies has some form of chromosomal abnormality.

There are two main types of chromosomal abnormalities. The former are structural abnormalities, meaning that the structure of individual chromosomes is somehow damaged or scrambled. The others are numerical anomalies. A normal baby has 46 chromosomes, created with two sets of 23 chromosomes inherited from the parents, and an unusual number of chromosomes can cause serious birth defects. The medical term for a numerical abnormality is "aneuploidy."

Many chromosomal abnormalities occur during fetal development because something goes wrong when cells duplicate. In the early stages of fetal development, cell replication proceeds at an incredibly fast rate, which means there are plenty of opportunities for replication errors. When chromosomal abnormalities develop after fertilization like this, they usually result in mosaicism, in which some cells have the abnormality and others do not.

A chromosomal abnormality can also occur before fertilization. If an error occurs during sperm and egg replication, this can lead to a chromosomal abnormality if the cell becomes part of a zygote, a fertilized egg that has the potential to develop into a fetus. As the cells in the zygote replicate, the chromosomal abnormality will replicate along with them.

Errors in structure include: deletion, duplication, inversion, insertion, and translocation. All of these errors result in some form of chromosomal coding. A section of a chromosome is missing, duplicated, flipped, added where it doesn't belong, or swapped with another section of the chromosome. Depending on the section and chromosome affected, such abnormalities can lead to serious birth defects or go unnoticed. Aneuploidy can take the form of trisomy, in which one chromosome pair has an extra chromosome attached, or monosomy, in which half of a chromosome pair is missing.

As a general rule, chromosomal abnormalities are not inherited as they arise from errors during cell duplication. The risk of chromosomal abnormalities increases with age, which is one reason why extensive prenatal testing is recommended for older mothers. However, it also occurs in younger women, and many miscarriages are the result of chromosomal abnormalities. In the event that a child or fetus is diagnosed with chromosomal abnormalities, several options are available and the situation can be discussed with a genetic counselor.

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