Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which process is NOT associated with the disruption of DNA structure?

1. Breakage

2. Nondisjunction

3. Substitution

4. Deletion

The correct answer is: Substitution

Substitution refers to a specific type of mutation where one nucleotide base is replaced by another. This process typically does not disrupt the overall structure of the DNA molecule but rather alters the genetic information encoded within it. Substitutions can lead to changes in the amino acid sequence of proteins, which may have functional consequences, but they do not typically involve breaking or rearranging the DNA backbone. In contrast, breakage refers to a physical disruption of the DNA strand, while nondisjunction specifically involves the failure of homologous chromosomes to separate properly during cell division, resulting in the incorrect distribution of chromosomes. Deletion involves removing a section of DNA, which can impact genetic function and structure. Both breakage and deletion directly alter the DNA structure, and nondisjunction can lead to aneuploidies that affect the genome's integrity. Thus, substitution stands out as the process that primarily affects genetic coding without disrupting the DNA's structural integrity.