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

What occurs when a base is left out in a DNA sequence?

1. Insertion

2. Nondisjunction

3. Deletion

4. Breakage

The correct answer is: Deletion

When a base is left out in a DNA sequence, it results in a deletion. This type of mutation occurs when one or more nucleotide bases are omitted from the DNA strand. As a result, the sequence is shortened, which can lead to significant changes in how genes are expressed. Deletions can have various effects on protein synthesis, depending on the location of the missing base. If the deletion occurs within a coding region or a regulatory element, it can disrupt normal biological functions and potentially lead to diseases. Understanding how deletions impact genetic information is crucial in fields like genetics and molecular biology, as they can influence everything from hereditary traits to susceptibility to genetic disorders. In contrast, insertion refers to the addition of extra bases, nondisjunction involves errors in chromosome separation during cell division, and breakage pertains to physical breaks in the DNA strand, which have different implications on genetic integrity. Thus, the identification of a base omission as a deletion helps clarify the consequences of such changes in DNA structure.