Multiple choice

Down syndrome involves an abnormality of chromosome pair number

  1. 3

  2. 11

  3. 21

  4. 23

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In most Down syndrome cases, there is an extra chromosome 21 (i.e. trisomy-21). More rarely, there is a structural modification in one or both of the chromosomes in this homologous pair.