What chromosomal condition is most associated with the karyotype 46,XX,der(14;21)(q10;q10),+21?

The karyotype 46,XX,der(14;21)(q10;q10),+21 indicates the presence of an additional chromosome 21, which is characteristic of Down syndrome, also known as trisomy 21. In this specific karyotype, the notation “+21” signifies that there is an extra copy of chromosome 21, leading to the genetic condition known as Down syndrome.

The term "der(14;21)" signifies a derivate chromosome resulting from a translocation between chromosomes 14 and 21, which can occur when there is a Robertsonian translocation. A Robertsonian translocation can lead to Down syndrome if it involves chromosome 21 and can cause individuals to inherit an extra chromosome 21 in a viable gamete.

Understanding the genetic basis of Down syndrome is crucial, as it helps in identifying affected individuals and providing appropriate care and support.