How is tthe stability of DNA of the species ensured?
DNA is the hereditary material of all the organisms. So, it is necessary for the organisms to ensure DNA stability to maintain their species integrity. Nature follows various methods to ensure that DNA remains stable for a particular species with very few minor variations (which are necessary for evolution). Some of these are:
1) DNA replication is highly efficient process: DNA polymerase, the enzyme which carries out DNA replication, is a very efficient molecule with a very low error rate. It has proof-reading ability; it checks each and every base after addition and removes it, if a wrong base is added. So, it ensures that the daughter DNA formed is exact replica of the parent DNA. Hence helps in stabilizing the DNA of the organism.
2) Cell cycle stops if DNA is damaged: If due to any reasons the DNA of a particular cell is damaged then the cell cycle stops at that phase and the cell does not replicate further and dies. So, this ensures that unstable DNA or modified or damaged DNA is not passed onto other cells.
3) Chromosomal number is maintained during reproduction. To ensure that all the individuals of a species have same number of chromosomes, the chromosomal number is maintained during reproduction.
- Asexual reproduction : here the parent cell reproduces to form exact replica of itself. So, chromosomal number is maintained as both the parent and daughter cells have same number of chromosomes.
- Sexual reproduction : It involves fusion of two kinds of gametes to form the offspring. Hence to maintain a stable chromosomal number, the number of chromosomes is halved during the formation of gametes . So, on fusion of two gametes we get the same chromosomal number as that of the parent.
So, these ensure that the chromosomal number or the DNA of an organism is stable.