there can be more than 2 chromosomes. for example, Down syndrome or trisomy 21 has 1 extra chromosome 21 causing down syndrome. in others, one chromosome could be taller or shorter than its pair by deletion or insertion. another way is having one of the chromosomes missing. in a specific disorder (don't remember which) a female has a missing X which means she only has one causing her to not develop breasts or the hip-widening most girls experience as they grow. sorry if this is not the answer you were looking for.
