Question

Describe in detail how insertion, deletion, and base substitution of nucleotides can have a significant impact on genes. Find three specific examples(actual gene mutations, not chromosome mutations) of ways in which a very small change in DNA can have a major impact on an organism, and describe each mutation in detail.

Answer 1

Insertion: In this mutation extra DNA base pairs are inserted into a new place or in the genes. The number of base pairs inserted can be one or many. Example: Huntington's disease in which nerve cells in the brain die and lead to involuntary movements, mental and cognitive abilities decreases. The Huntingtin gene codes a protein called ‘huntingtin’ which is having CAG (cytosine-adenine-guanine) triplet repeats, this repeat duplicates and expands producing more triplet inserts , resulting in abnormal protein folding leading to nerve cell damage

Deletions: In this mutation some part of gene or a length of nucleotides is deleted, it may range from one to thousands. Example: cri du chat (French for "cry of the cat") syndrome, named for the distinctive cry affected infants make due in part to malformations of the larynx. Some part of three genes Semaphorine F (SEMA5A) and delta catenin (CTNND2), Telomerase reverse transcriptase, involved in cerebral development and larynx development   

Substitution: It’s a mutation where one base pair is replaced/substituted by another base pair, for example in sickle cell anaemia disease, change in a “single letter code” (nitrogen base lets say on sense strand of DNA producing mRNA if Adenine (A) is replaced by Thiamine (T)) results in change in a codon to one that encodes a different amino acid and cause a change in the protein produced. In Sickle Cell Anaemia codon GAG mutates to GTG resulting in change in amino acids Glutamate to Valine, resulting in complete change in the folding pattern of haemoglobin and red blood cell acquires the shape of a ‘sickle’ instead of concave shape, which in turn affects oxygen carrying ability and patients suffers from anaemia.