[Partial trisomy 21 (21q21 - 21q22.2)].

Area of Science:

• Genetics
• Human Genetics
• Cytogenetics

Background:

• Trisomy 21 syndrome, also known as Down syndrome, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.
• The syndrome is associated with characteristic facial features, intellectual disability, and developmental delays.

Observation:

• A case study of a child exhibiting a phenotype strongly resembling trisomy 21 syndrome.
• Genetic analysis revealed an abnormal chromosome 21, specifically a duplication of the segment 21q21 to 21q22.2.

Findings:

• The observed phenotype was attributed to partial trisomy of chromosome 21.
• Comparison with other partial and complete trisomy cases suggests that the critical region for the characteristic features of trisomy 21 syndrome, including intellectual disability, is located at 21q22.2.

Implications:

• This finding helps to refine the understanding of genotype-phenotype correlations in trisomy 21.
• Identifies specific chromosomal regions responsible for key features of Down syndrome, aiding in genetic counseling and research.