Dennis is mentally retarded. He has a flat nose, a protruding tongue, and upwardly slanted eyes. Which of the following statements is most likely to be true A)Dennis has Down syndrome, caused by an extra 21^st chromosome. B)Dennis has Down syndrome, caused by missing 21^st chromosome. C)Dennis has Down syndrome, caused by maternal alcohol consumption. D)Dennis has Down syndrome, caused by a lack of oxygen during birth.

Question

Quizplus · Accepted Answer

Dennis's described features are characteristic of Down syndrome, which is most commonly caused by the presence of an extra chromosome 21 (trisomy 21), not by a missing chromosome, maternal alcohol consumption, or lack of oxygen during birth.

Dennis Is Mentally Retarded