The direction of shell coiling in snails such as Limnea peregra is determined by the egg's genotype,which affects orientation of the spindle in early cleavage divisions.How could the egg genotype cause the directional orientation of a spindle in the embryo?
A)by products of mitochondrial genes that pull the centrioles toward the mitochondrial position
B)by attachment of spindle fibers to mitochondria at the edges of the cell
C)by maternally directed placement of mRNAs and proteins at appropriate positions in the egg cytoplasm
D)by the release of maternal mitochondrial genomes into the egg cytoplasm
E)by zygotic gene activation due to maternal mitochondrial genes

Question

Quizplus · Accepted Answer

The egg carries maternally derived mRNAs and proteins that are distributed asymmetrically in the cytoplasm, leading to the activation of specific genes and signaling pathways during development. This results in the orientation of the spindle during early cleavage divisions, which in turn determines the direction of shell coiling in snails such as Limnea peregra.

The Direction of Shell Coiling in Snails Such as Limnea