Final answer:
An Internal Ribosome Entry Site (IRES) is a functional region of an mRNA molecule that allows for the initiation of translation independently of the 5' cap structure. It provides an alternative mechanism for initiation of protein synthesis.
Step-by-step explanation:
An Internal Ribosome Entry Site (IRES) is a functional region of an mRNA molecule that allows for the initiation of translation independently of the 5' cap structure.
It provides an alternative mechanism for initiation of protein synthesis in situations where the traditional cap-dependent scanning mechanism is hindered or not available. The IRES is typically found in viral or cellular mRNAs and plays a crucial role in modulating gene expression.