Which one of the following causes a frame- shift mutation?
**Core Concept**
A frameshift mutation is a type of genetic mutation that occurs when the reading frame of the genetic code is altered, resulting in a completely different amino acid sequence. This type of mutation is often caused by the insertion or deletion of nucleotides in a DNA sequence, which changes the reading frame of the genetic code.
**Why the Correct Answer is Right**
Frameshift mutations occur when the number of nucleotides inserted or deleted is not a multiple of three, which disrupts the reading frame of the genetic code. This results in a completely different amino acid sequence being translated from the affected gene. In the case of a frameshift mutation, the genetic code is read in a different frame, leading to a new set of amino acids being synthesized. This can result in a nonfunctional protein or a protein with a completely different function.
**Why Each Wrong Option is Incorrect**
**Option A:** Point mutations, such as transitions and transversions, do not cause frameshift mutations.
**Option B:** Gene duplication, where a gene is copied, can lead to gene amplification but does not cause frameshift mutations.
**Option C:** Gene silencing, where the expression of a gene is reduced or eliminated, is not a type of mutation that causes frameshift mutations.
**Clinical Pearl / High-Yield Fact**
Frameshift mutations are often caused by errors during DNA replication or repair, and can result in a wide range of genetic disorders, including genetic diseases and cancer.
**Correct Answer: C. Frameshift mutations occur when the number of nucleotides inserted or deleted is not a multiple of three, disrupting the reading frame of the genetic code.**