All of us are made up of cells, in the nucleus of each cell are thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times along with proteins. The study of these chromosomes is called Cytogenetics.
In humans the normal cell nucleus contains 46 chromosomes, made up of 22 pairs of autosomes and a single pair of sex chromosomes (allosomes) – XX in female and XY in the male. One member of each of these pairs is given by each parent.
Normal Male Karyotype (46, XY)
Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labelled the “p arm.” the long arm of the chromosome is labelled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape. Based on the size and centromeric position the chromosomes are arranged in to a karyotype.
Any changes in chromosome number or structures may be associated with anomalies.