How does mutation affect DNA replication?

Hint: Mutation is the word which means change in the original helical structure of the DNA. Mutations occur in the sequence of the DNA which is generally noticed in the structure during the process of copying which sometimes mistakenly or by external factors results in change in number of chromosomes or mutation.

Complete answer:
Mutations means change in the genetic material that would be inherited. Mutation in chromosomes may change the way genes are expressed. DNA replication is the process by which a cell makes an identical copy of its genome before it divides. But during the making of its copy sometimes mutations occur which results in abnormal numbers of chromosomes that can cause deadly diseases like one of the best examples of ‘trisomy’. In this disease number of chromosomes are altered as 21. These mutations can also be caused by exposure to environmental factors such as smoking, sunlight and radiations. Cancer is also the most common genetic disease which is caused by mutations occurring in a number of growth-controlling genes. Mutations arise spontaneously at low frequency owing to the chemical instability of purine and pyrimidine bases. Consider that every time a human cell divides and its DNA replicates, it has to copy and transmit the exact same sequence of 3 billion nucleotides to its daughter cells. Also, nothing is perfect while most DNA replicates with fairly high fidelity, mistakes do happen, with polymerase enzymes sometimes inserting the wrong nucleotide or too many or too few nucleotides into a sequence.

Note: Most of these mistakes or mutations are fixed through various DNA repair processes. Repair enzymes recognize structural imperfections between improperly paired nucleotides, cutting out the wrong ones and putting the right ones in their place.