**Core Concept**
Gene duplication is a process where a gene is copied and replicated in the genome, resulting in identical copies of the same gene. This event can occur through various mechanisms, including errors during DNA replication, viral infections, or other genetic anomalies. Gene duplication can lead to the creation of new genes, which can then undergo mutations and evolve into new functional genes.

**Why the Correct Answer is Right**
Gene duplication is a crucial mechanism in the evolution of new genes and proteins. It allows for the creation of new genetic variation, which can then be subject to natural selection and lead to the development of new traits and functions. This process is particularly important in the evolution of complex organisms, as it provides a means for the creation of new genes that can adapt to changing environments and ecological niches. Gene duplication can also lead to the creation of gene families, where multiple copies of a gene are present and can perform different functions.

**Why Each Wrong Option is Incorrect**
**Option A:** Gene duplication is not primarily responsible for the evolution of antibiotic resistance. While gene duplication can lead to the creation of new genetic variation, the evolution of antibiotic resistance is more closely related to the process of horizontal gene transfer and the selection of existing genetic variation.
**Option B:** Gene duplication is not directly responsible for the evolution of cancer. While gene duplication can lead to the creation of new genetic variation, the evolution of cancer is more closely related to the accumulation of mutations and epigenetic changes in existing genes.
**Option C:** Gene duplication is not primarily responsible for the evolution of genetic disorders. While gene duplication can lead to the creation of new genetic variation, the evolution of genetic disorders is more closely related to the inheritance of mutant alleles and the disruption of normal gene function.

**Clinical Pearl / High-Yield Fact**
Gene duplication can lead to the creation of gene families, where multiple copies of a gene are present and can perform different functions. This process is particularly important in the evolution of complex organisms, as it provides a means for the creation of new genes that can adapt to changing environments and ecological niches.

**Correct Answer:** C. Gene duplication is primarily responsible for the evolution of new genes and proteins, particularly in complex organisms.