A
typical human karyotype has 23 types of chromosomes arranged from largest to
smallest. In males and females 22 of these chromosomes look exactly the same
and they are called autosomes. The 23rd pair of chromosomes is the sex
chromosome which differentiates males from females. Females have 2 copies of
the x chromosome. Males have a copy of both x and y chromosome to make the 23rd
pair.
Chromosomes can also have abnormalities that
result to different conditions and identifiable traits. A most common
chromosomal abnormality is the condition called Down Syndrome, where chromosome
21 has a third copy because of an abnormal cell division.
