Which of the following refers to regionally localized proteins or mRNAs in an unfertilized egg that regulate development
Unfertilized eggs establish developmental asymmetry through regionally localized cytoplasmic determinants composed of maternal mRNAs, regulatory proteins and organelles tethered to the cytoskeleton at specific cortical domains. Examples include bicoid mRNA anchored anteriorly in Drosophila oocytes and VegT and Vg1 localized vegetally in Xenopus. Upon fertilization and cleavage, daughter blastomeres inherit different quantities of these factors, which activate selective transcription factor cascades before zygotic genome activation. This prelocalized information underlies autonomous specification, establishing body axes, germ layers and cell polarity without requiring immediate cell-cell signaling or external gradients.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 2: Cytoplasmic Determinants and Maternal Effect Genes.