nonreciprocal translocation

A one-way translocation in which a chromosomal segment is transferred to a nonhomologous chromosome.It is an unbalanced translocation.
Translocation is a change in position of a chromosomal segment to another region of the same chromosome or to another chromosome.
In an unbalanced translocation, there is an extra piece of one chromosome and/or a missing piece of another chromosome. An affected child may have learning disabilities, developmental delay, and health problems. The seriousness of the disability depends on exactly which parts of which chromosomes are involved and how much missing or extra chromosome material there is.

(Comparison: exchange of portions of chromosomes)
• nonreciprocal translocation: One-way transfer of a chromosomal segment to another chromosome.
• reciprocal translocation: Portions of two chromosomes are simply exchanged with no net loss of genetic information.
• Robertsonian translocation: The entire long arms of two different chromosomes become fused to each other. The short arms also join to form a smaller reciprocal product, which typically contains only nonessential genes also present elsewhere in the genome, and is usually lost within a few cell divisions (reduced chromosome number from 23 to 22). Therefore, affected individuals have only 45 chromosomes in each of their cells, yet all essential genetic material is present, and they appear normal. Their children may either be normal, carry the fusion chromosome (depending which chromosome is represented in the gamete), or they may inherit a missing or extra long arm of an acrocentric chromosome (phenotype affected).

(Comparison: inheritance of genetic materials)
• unbalanced translocation: Some of the zygotes die in utero. A fetus inherits a chromosome with extra or missing genetic material from a parent with a balanced translocation.
• balanced translocation: No genetic material is lost during the exchange. Patients with reciprocal translocation may have a normal phenotype, but this chromosomal abnormality can result in abnormal meiosis. The resulting sperm are more likely to have aneuploidy, which can manifest with recurrent pregnancy loss.

Cf. intrachromosomal translocation, interchromosomal translocation, chromosomal fusion