Even though there is no family history of disorder or abnormalities in the case of Pedigree #2 and none of the parents is a carrier of the disease or alleles, the offspring exhibits the disorders. Determination of the actual genesis of the disorder would be the most puzzling given that none of the parents carries the disease or the alleles in this scenario. Nevertheless, revelation about the possible causes of the chromosomal disorders is of great help towards the understanding of genetic alterations under the influence of various environmental and external factors. Such external factors which can induce chromosomal mutations include exposure to carcinogenic substances and high ultraviolet radiation from the sun.
According to Howard D. Beardmore (2010), exposure to carcinogenic chemical substances like Hydroxylamine, ochratoxin A metabolites and other oxidative detergents can significantly alter the molecular structure of the chromosomes in an individual subject. These chromosomal alterations could take the forms of insertions, deletions, translocations and loss of heterozygosity. In his publication, The Mutation, Howards gives genetic accounts to explain causes of abnormalities in the case of Pedigree #2.
The mechanisms of chromosomal alterations differ from one form to another as explained by Howard (2010). In the commonest point mutation, nucleotides could be interchanged due to transversion of the constituent amino acids and bases thus causing a serious error in the resultant codon codes within the nucleotide. In the same manner, insertion removes one or more nucleotide into a DNA molecule. The intensified levels of insertions amount to amplification. On the flipside, deletion results into loss of one or more nucleotide(s) from the DNA. Coupled with the loss of heterozygosity by the alleles during the non-dysjunctional meiotic sexual recombination, chromosomal alterations is the number one cause of disorder or abnormalities in Pedigree #2 which determines the pattern of inheritance (Howard 2010).