Chromosome are the most significant of all cell components. They are the carrier of genes and in that they control hereditary and variation. Chromosome were first observed by Hofmeister (1849) in the pollen mother cells of Tradescantia. But, the term chromosome was introduced by Waldeyer (1988). There exists a sharp distinction between prokaryotic and eukaryotic chromosome. Prokaryotic chromosome is very simple and composed of a single DNA molecule. Eukaryotic chromosome is highly complex with different components, namely DNA, RNA, basic proteins and nonbasic proteins. there are two kinds of eukaryotic chromosomes, namely autosomes and sex chromosomes. Autosomes carry the genes which control somatic or non sexual characters, and sex chromosomes contain the genes which control sexual characteristics.
Prokaryotic chromosome vs Eukaryotic Chromosome
1. Primarily haploid
2. DNA is not complexed with proteins
3. The basic proteins histones are altogether absent.
4. Chromosomal DNA is localized in the cytoplasm.
5. Chromosomal DNA is a closed circular polymer
6. No definite morphological stage for DNA replication.
1. Primarily diploid
2. DNA is complexed with proteins forming deoxyribonucleoprotein
3. Histones are chacteristically present.
4. Chromosomal DNA is confined within the nucleus.
5. Chromosomal DNA is a linear polymer
6. DNA replication occurs in the S phase of mitotically cycle.