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Satellited 4q identified in amniotic fluid cells
I Miller1, G Songster, S Fontana
1Molecular and Clinical Cytogenetics Laboratory, Stanford University Medical Center, California, USA.
American Journal of Medical Genetics
|January 16, 1995
Summary
A genetic anomaly, specifically extra material on chromosome 4 (4qs), was identified in a fetus and the father. This familial chromosome 4 abnormality, involving ribosomal DNA, appears to be inherited through generations without causing disease.
Area of Science:
- Human Genetics
- Cytogenetics
- Reproductive Genetics
Background:
- Prenatal diagnosis identified an extra chromosomal segment on the long arm of chromosome 4 (4qs) in fetal amniotic fluid.
- The fetus exhibited no visible loss of material from chromosome 4 or evidence of a balanced rearrangement.
Purpose of the Study:
- To investigate the origin and inheritance pattern of the extra material on chromosome 4 (4qs).
- To determine if the observed chromosomal anomaly in the fetus was inherited and assess its potential phenotypic impact.
Main Methods:
- Karyotyping of amniotic fluid and paternal peripheral blood.
- Fluorescence in situ hybridization (FISH) using ribosomal DNA probes.
- Analysis of familial inheritance through extended family studies.
Main Results:
- The identical 4qs chromosome was found in the father, indicating an inherited unbalanced rearrangement.
- Ribosomal DNA was confirmed at the terminus of the 4qs chromosome in the fetus, father, and paternal grandmother.
- The anomaly was present in phenotypically normal individuals across at least three generations.
Conclusions:
- The satellited 4q chromosome likely resulted from a translocation event with minimal or no loss of 4q material.
- This derivative chromosome 4 represents a familial, inherited anomaly that does not appear to cause a discernible phenotype in carriers.