hereditary material in living organism is deoxyribose nucleic acid (DNA)molecule.DNA structure exist as a double stranded,coiled into the shape of double helix .unit of discrete traits is called gene. genes are set in chromosomes,chromosomes itself is a sructure of DNA and protein that is found in nucleus. the set up of DNA and protein combination into chromosomes iis called chromatin .a place in a chromosome where gene exist is called locus.
there are two types os chromosomes in organism , which are:
- somatic chromosome (autosome )which does not determine sexsual characteristic
- sex chromosome (gonosome or alosome) which determines sexsual characteristic. for example, there are 22 pairs of autosome and a pair of gonosome in human cell. human gonosome consist of X chomosome and Y chromosome . if the pair of gonosome is XY ,then the individual is male. however, if the pair of gonosome is XX, then the individual is female