(a) The two cells formed after DNA copying are similar but not identical.What reason can be associated for this?
(b) Variation though leads to certain changes in an individual but is useful for the survival of species over time. Justify this statement.
(c) Is the consistency of DNA copying important during reproduction?

Dear student.

Please find the solution below:

21. a.  This means that during the process of replication of DNA, the number of copies produced after each replication step will be equal or similar and most of the base sequences in the new copy will be similar or same to the original, but due to little error in the copying of DNA, variations in the DNA will be produced each time i.e the DNA copies generated may or may not be identical to the original DNA.

b. 

• Variation is the differences in the traits shown by the individuals of a species, and also by the offsprings (siblings) of the same parents.
• Variations help the species more adapted to survive with the changing conditions and it helps for the survival of the species.

But, variation is not beneficial for the individual. Because certain variations may not give any advantage to an individual organism, in particular environmental conditions. If an individual organism naturally accumulates variation in its gene composition through mutation or any other source could be harmful and may lead to death of an individual. Thus variation at individual level is not beneficial as an individual does not evolve by these variations.

c. DNA has the blueprint of life. In other words, how the organism will look, how the organism will adjust with its environment, what will be the function of each cell of the body—every tiny information about the organism is encoded in the DNA. This vital biomolecule is duplicated during cell division and is also passed on, through the gametes, to the next generation during reproduction. The integrity and consistency of this biomolecule is thus of supreme importance to the continuity of the species. Seemingly minor errors during copying of DNA may lead to huge repercussions in the form of physical deformity of the offspring. Thus exact copying of DNA is done to facilitate stability of population of any species.

Regards.