Sherry, a 3-Year-Old, Has an Extra Copy of Chromosome 21

Short Answer

Sherry, a 3-year-old, has an extra copy of chromosome 21. She is often made fun of by other children because of her unusual looks; she has a round face and her skull is flat. She has a protruding tongue, and she finds it difficult to play because of her short limbs. Her parents find that her mental abilities are impaired when compared with other children her age. Sherry is most likely suffering from a chromosomal abnormality called ________.