10 Questions
What is the primary cause of full trisomy 21?
Meiotic nondisjunction
Approximately what percentage of full trisomy 21 cases occur due to paternal nondisjunction during spermatogenesis?
5%
What is the karyotype of a male individual with full trisomy 21?
47,XY,+21
In translocation trisomy 21, which chromosome is most commonly attached to chromosome 21?
Chromosome 14
What is the approximate percentage of cases where a balanced translocation is inherited from a parent in translocation trisomy 21?
50%
What is the karyotype of an individual with a balanced Robertsonian translocation?
45,XX,t(14;21)
What is the result of an unbalanced Robertsonian translocation?
Three copies of genetic material from chromosome 21
What is the cause of mosaic trisomy 21?
Nondisjunction during mitosis
What determines the phenotypic expression of mosaic trisomy 21?
The ratio of healthy to trisomic cells
What is the karyotype of an individual with mosaic trisomy 21?
46,XX/47,XX,+21
Learn about the causes of Down Syndrome, specifically full trisomy 21, including its definition, occurrence, and pathogenesis. Understand the role of meiotic nondisjunction and its effects on chromosome 21.
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