DNA, RNA, Chromosomes, and GenesChromosomes |
Can people have missing or extra chromosomes? |
Yes, people can live with this chromosomal abnormality, depending on which chromosomes are copied or missing; for example, Down syndrome (an extra copy of chromosome 21) and Turner syndrome (a female with only one X chromosome). Conversely, almost 1 percent of all conceptions are triploid (three copies of each chromosome), but over 99 percent of these die before birth.