Discriminant functions and 21-trisomy mosaicism

Area of Science:

• Genetics
• Dermatoglyphics
• Human Biology

Background:

• Down syndrome, caused by trisomy 21, presents with varying genetic compositions, including mosaicism.
• Dermatoglyphic patterns (fingerprints, palm lines) are influenced by genetic factors and can differ in individuals with chromosomal abnormalities.
• Distinguishing between complete trisomy 21 and 21-trisomy mosaicism is crucial for accurate diagnosis and genetic counseling.

Purpose of the Study:

• To develop discriminant functions using dermatoglyphic characters to differentiate 21-trisomy mosaicism from normal controls and complete 21 trisomy.
• To assess the effectiveness of these discriminant functions in separating mosaic individuals from control groups.
• To explore the potential application of discriminant function indices in genetic counseling and the study of parental populations.

Main Methods:

• Utilized Fisher's method to select optimal sets of ten dermatoglyphic characters for discriminant analysis.
• Calculated mean discriminants and discriminant coefficients for 173 cases of 21-trisomy mosaicism, 225 cases of complete 21 trisomy, and 302 normal controls.
• Constructed distribution curves of individual discriminants for all three groups.

Main Results:

• Discriminant functions successfully separated 21-trisomy mosaicism from normal controls, with mean discriminant values closer to the Down syndrome group.
• The separation achieved between mosaics and normal controls exceeded two standard deviations.
• The distribution curve for mosaics was bimodal, suggesting a potential relationship between dermatoglyphic patterns and cytogenetic findings.

Conclusions:

• Dermatoglyphic discriminant functions provide a valuable tool for distinguishing 21-trisomy mosaicism from normal individuals.
• The findings support the use of these discriminant function indices in genetic counseling and for identifying potential undetected mosaics in parental populations.
• Further research with larger sample sizes is needed to confirm and refine these preliminary results.