Down syndrome results from which of the following chromosomal abnormalities
Down syndrome results from which of the following chromosomal abnormalities Down syndrome, a genetic condition characterized by intellectual disability and distinct physical features, results from a specific type of chromosomal abnormality. Under normal circumstances, human cells contain 23 pairs of chromosomes, totaling 46 chromosomes. These chromosomes carry the genetic blueprint necessary for growth, development, and bodily functions. However, in the case of Down syndrome, there is an extra copy of chromosome 21, leading to a total of 47 chromosomes in most cases.
This additional chromosome is the primary cause of Down syndrome and is usually the result of a nondisjunction event during cell division. Nondisjunction occurs when chromosomes fail to separate properly during the formation of either the egg or sperm. As a result, when fertilization occurs, the resulting embryo has an extra chromosome 21 in every cell. This form of Down syndrome is called trisomy 21 because it involves three copies of chromosome 21 instead of the usual two.
Down syndrome results from which of the following chromosomal abnormalities Trisomy 21 is the most common and well-studied chromosomal abnormality associated with Down syndrome, accounting for about 95% of cases. It is most often linked to maternal age, with a higher risk observed in pregnancies where the mother is over 35 years old. The precise biological reasons behind this increased risk are still being studied, but it is believed that the aging process in the ovum may contribute to the increased likelihood of nondisjunction.
Down syndrome results from which of the following chromosomal abnormalities Apart from trisomy 21, there are other, less common chromosomal abnormalities that can lead to Down syndrome. These include translocation and mosaicism. Translocation occurs when part of chromosome 21 becomes attached to another chromosome, usually chromosome 14 or 22. This abnormality can be inherited from a parent who carries a balanced translocation, meaning they have a rearrangement of genetic material but do not exhibit symptoms themselves. If a parent carries such a translocation, there is an increased risk of passing it on to the offspring, resulting in an extra copy of chromosome 21 material in the child’s cells.
Down syndrome results from which of the following chromosomal abnormalities Mosaic Down syndrome is another rare form, where some cells in the body have the usual 46 chromosomes, while others have 47 due to an extra chromosome 21. This mosaic pattern results from a nondisjunction event that occurs after fertilization, during early cell division. The severity and physical features of mosaic Down syndrome can vary widely depending on the proportion of affected cells.
Down syndrome results from which of the following chromosomal abnormalities Understanding the chromosomal basis of Down syndrome is crucial for diagnosis, genetic counseling, and management. Prenatal testing methods such as amniocentesis, chorionic villus sampling, and non-invasive prenatal testing (NIPT) can detect these chromosomal abnormalities early in pregnancy. Knowing the specific abnormality can aid families in making informed decisions and preparing for the needs of their child.
In summary, Down syndrome results primarily from trisomy 21, an extra chromosome 21 due to nondisjunction during cell division. Less commonly, it can arise from chromosome translocation or mosaicism, each affecting the genetic makeup differently but leading to similar developmental and physical characteristics associated with the syndrome. Down syndrome results from which of the following chromosomal abnormalities
