<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 3-year-old boy presents to a geneticist for generalized developmental delay. Upon presentation he is found to have a distinctive facial structure with prominent epicanthal folds and macroglossia. Further physical examination reveals a simian crease on his palms bilaterally. Based on these findings, the physician strongly suspects Down syndrome and obtains a karyotype. Surprisingly the karyotype shows 46 chromosomes with two normal appearing alleles of chromosome 21. Further examination with fluorescent probes reveals a third copy of chromosome 21 genes that have been incorporated into another chromosome. What is the name of this mechanism of Down syndrome inheritance?? A: Nondisjunction, B: Mosaicism, C: Robertsonian translocation, D: Imprinting, E: Anticipation,  <response>: This is a question about the genetic mechanism behind Down syndrome. The patient exhibits classic physical features of Down syndrome, which is caused by an extra copy of chromosome 21. However, the karyotype shows 46 chromosomes, so there is not an extra whole chromosome 21 ruling out nondisjunction. Further testing reveals a third copy of chromosome 21 genes incorporated into another chromosome. This describes a Robertsonian translocation, where the long arms of chromosome 21 get attached to another chromosome, resulting in extra copies of chromosome 21 genes without an extra standalone chromosome 21.C: Robertsonian translocation 