Chromosomal abnormalities occur due to the change in either chromosome number or chromosome structure. Deletion, duplication, translocation, inversion and addition are some of the structural chromosomal abnormalities while trisomy, tetrasomy and monosomy are numerical chromosomal abnormalities. What are Chromosomes? In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. Humans have 23 pairs of chromosomes, one from each parent. The most important function of chromosome is to carry the genetic material from one cell generation to the next. The basic shape of chromosomes is rod-shaped consisting of a centromere and arms. Chromosome Structure The chemical composition of a chromosome is histone proteins and DNA. Each cell has a pair of each kind of chromosome known as a homologous chromosome. Chromosomes are made up of chromatin, which contains a single molecule of DNA and associated proteins. Each chromosome contains hundreds and thousands of genes that can precisely code for several proteins in the cell. Structure of a chromosome can be best seen during cell division.
