Asexual reproduction usually results in the production of genetically identical offspring’s; the only genetic variation arises as a result of occasional inaccuracies in DNA replication (or DNA copying) at the time of cell division. This will become clear from the following discussion.
The material which carries genetic information from the parents to the offspring’s is DNA-Deoxyribo Nucleic Acid (which is present in the form of chromosomes in the nuclei of all the cells). The basis of asexual reproduction is mitosis.
This is the division of a nucleus into two identical daughter nuclei. Each daughter nucleus has the same genetic makeup because of the replication of DNA (or copying of DNA) of the parent cell.
After the division of the nucleus, the rest of parent cell divides to form two genetically identical daughter cells. The daughter cells can then form two offsprings. From this we conclude that all the offsprings produced by one parent as a result of asexual reproduction are usually genetically identical.
The new organisms (or offsprings) produced by one parent through asexual reproduction (which are genetically identical to the parent) are called clones. The clones possess exact copies of the DNA (or genes) of their parent and hence show remarkable similarity to the parent and to one another. Thus, asexual reproduction produces genetically identical offsprings called clones.
For example, when a parent Hydra reproduces by the asexual method of budding, the new Hydrae (or offsprings) formed are clones (which are genetically identical to the parent Hydra as well as to one another).
Similarly, when we are using a cutting to grow a new plant, we are making a clone. The cutting of a plant contains the same DNA (or genes) as the original plant (or parent plant). This cutting will grow into an exact copy of the original plant. So, a clone is formed.
The clones of plants can be produced by the asexual methods of reproduction such as cuttings, layering, grafting, tissue cultic etc. These days techniques have been developed to clone even animals. Dolly the sheep hit the headlines in 1997 as the first successfully produced animal clone. The process of producing genetically identical new organisms (or offsprings) by asexual reproduction methods is called cloning.
We will now explain how slight variations are introduced in asexual reproduction. The replication (or copying) of DNA in the cell is done by certain biochemical reactions which synthesize more of genetic material. No biochemical reaction can reproduce 100 per cent same results.
So, when the DNA already present in the nucleus of the parent cell is replicated (or copied) by making more DNA at the time of asexual reproduction, then slight variations come in the two copies formed.
Due to this, the two DNA f molecules formed by replication will be similar but may not be exactly identical to the original DNA. These E slight variations in the replication of DNA molecule will lead to slight variations in the offsprings produced by asexual reproduction.
From the above discussion we conclude that the importance of DNA replication (or DNA copying) in asexual reproduction is that slight variations may arise in the offsprings in respect to the parent organism. So, although the offsprings produced by asexual reproductions are said to be genetically the same as the parent organism, but still they have occasional variations.
This means that the organisms do not always create exact copies of themselves in asexual reproduction. Please note that the importance of DNA copying in asexual reproduction is that the characteristics of the parent organisms are transmitted to its offsprings i and at the same time some occasional variations are also produced in the offsprings. We will now describe the importance of variations introduced in reproduction.
The importance of variations in organisms introduced during reproduction is that it helps the species of various organisms to survive and flourish even in adverse environment. This will become clear from the following discussion. There may be some drastic changes like excessive heat or cold or shortage of water (drought), etc., in the habitat of a species of organisms. Now, if all the organisms of a population living in that habitat are exactly identical, then there is danger that all of them may die and no one would survive under .those conditions.
This will eliminate the species from that habitat completely. However, if some variations are present in some individual organisms to tolerate excessive heat or cold or survive on meagre water supply, then there is a chance for them to survive and flourish even in adverse environment. In this way, the introduction of variations during reproduction provides stability to the populations of various species by preventing them from getting wiped out during adverse conditions.
For example, if there is a population of certain bacteria living in temperate water (which is neither very hot nor very cold) and the temperature of water increases too much due to global warming, then most of these bacteria will not be able to tolerate excessive heat and hence die. But some bacteria which had variations to resist heat would survive and grow further.