Human chromosome variation with two Robertsonian translocations.

Area of Science:

• Genetics
• Human Genetics
• Cytogenetics

Background:

• Robertsonian translocations are balanced chromosomal rearrangements involving fusion of two acrocentric chromosomes.
• These rearrangements can lead to aneuploidy in offspring, often resulting in conditions like Down syndrome.
• Understanding the inheritance and phenotypic outcomes of complex chromosomal rearrangements is crucial for genetic counseling.

Observation:

• A female individual was identified with two distinct Robertsonian translocations: t(14q21q) and t(14q22q).
• She also exhibited XX/XXX sex chromosome mosaicism.
• Both translocations were monocentric and lacked rRNA activity via silver staining.

Findings:

• The t(14q21q) translocation was familial, identified through a nephew with Down syndrome.
• The t(14q22q) translocation's origin was undetermined.
• The woman had two pregnancies, each resulting in a child inheriting one of the translocations; both children were phenotypically normal.

Implications:

• This case highlights the potential for phenotypically normal individuals to carry complex chromosomal rearrangements.
• It demonstrates that inheritance of two different Robertsonian translocations does not necessarily lead to adverse outcomes.
• The findings contribute to the understanding of Robertsonian translocation inheritance, risk assessment, and genetic counseling for families with chromosomal abnormalities.