Final answer:
Piwi-interacting RNAs (piRNAs) are the small noncoding RNAs responsible for reestablishing methylation patterns during gamete formation and blocking the expression of transposons, linked to genome stability and gene silencing.
Step-by-step explanation:
The type of newly discovered small noncoding RNAs that reestablish methylation patterns during gamete formation and block the expression of some transposons are known as piRNA.
Piwi-interacting RNAs (piRNAs) play a crucial role in the silencing of transposable elements and maintaining the stability of the genome in germ cells. Unlike microRNAs (miRNAs) and small interfering RNAs (siRNAs), piRNAs associate with Piwi proteins, which are a subset of the Argonaute family. These molecules are typically 24-31 nucleotides long and are involved in the defence against genomic instability caused by transposons. They also function in the epigenetic regulation of gene expression, including the reestablishment of DNA methylation during gamete formation, ensuring the proper development of future generations. This process of gene silencing is part of a broader mechanism known as RNA interference (RNAi), where small noncoding RNAs downregulate gene expression by various methods, including mRNA degradation and inhibition of translation.