What is the outcome of having an extra chromosome, as seen in trisomy 21?

The presence of an extra chromosome, such as in trisomy 21, is associated with a condition commonly known as Down syndrome. This genetic anomaly typically results in a variety of physical and developmental challenges. Individuals with Down syndrome often exhibit distinct physical features, including a flattened facial profile, slanted eyes, and a short neck, as well as a range of cognitive impairments that can affect learning and development.

In addition to physical traits, the developmental challenges may include delays in speech and language development, social interaction difficulties, and increased risk for certain medical conditions, such as heart defects and gastrointestinal issues. Thus, the overarching effect of having an extra chromosome in this context significantly influences the individual's overall health and development, justifying the selection of this option as the correct answer.