Final answer:
The accompanying figure shows how levels of a microRNA called miR-320b change with age in the prefrontal cortex of the brains of humans, chimps, and macaques (African monkeys). This may be important for understanding the genetic features that make us human, because microRNAs 3) influence gene expression by binding to messenger RNAs.
Step-by-step explanation:
MicroRNAs (miRNAs) are small RNA molecules that play a crucial role in gene regulation by influencing gene expression. The correct option is 3) "influence gene expression by binding to messenger RNAs." In the figure provided, the changes in levels of miR-320b with age in the prefrontal cortex of humans, chimps, and macaques suggest a potential role in the genetic features that differentiate humans from other primates.
miRNAs function by binding to messenger RNAs (mRNAs), thereby regulating the translation of these mRNAs into proteins. The age-related changes in miR-320b levels may indicate its involvement in the aging process or other aspects of neural development.
MicroRNAs are not exclusive to primates (Option 1). They are a widespread class of molecules found in various organisms. Additionally, miRNAs do not translate into polypeptides (Option 2); instead, they primarily act as post-transcriptional regulators of gene expression. Options 4 and 5 are also incorrect, as miRNAs are not exclusively transcribed from "selfish DNA" sequences like Alu elements, and their role in increasing neuronal connectivity and intelligence is a complex and multifaceted aspect of neurobiology.
In summary, the correct answer is 3) "influence gene expression by binding to messenger RNAs," highlighting the important regulatory role of microRNAs in genetic processes.