Chromosomal Disorders Practice Test

A 1-month-old infant has a high-pitched cry, microcephaly, and hypotonia. Karyotype shows 46,XY,del(5)(p15). The parents ask what type of chromosomal change this represents compared with trisomy 21. Which statement best explains the difference?

A 4-day-old newborn with hypotonia and facial features consistent with Down syndrome undergoes chromosomal testing. Karyotype shows 46,XX with three copies of chromosome 21 material due to a translocation. The genetic counselor asks about parental testing. Which parental finding would most increase recurrence risk in future pregnancies?