Answer: diffusion
Bicoid is a maternal effect gene whose protein concentration gradient patterns the anterior-posterior axis during Drosophila embryogenesis. Bicoid was the first protein demonstrated to act as a morphogen. Although Bicoid is important for the development of Drosophila and other higher dipterans it is absent from most other insects where its role is accomplished by other genes.
One of the best understood examples of pattern formation is the patterning along the future head to tail (antero-posterior) axis of the fruit fly Drosophila melanogaster. There are three fundamental types of genes that give way to the developmental structure of the fly: maternal effect genes segmentation genes and homeotic genes. The development of Drosophila is particularly well studied and it is representative of a major class of animals the insects or insecta. Other multicellular organisms sometimes use similar …
Bicoid (gene) – Wikipedia
Cleavage – Wikipedia
Cleavage (embryo) – Wikipedia
Drosophila embryogenesis – Wikipedia
The egg cell cytoplasm contains localized mRNA molecules such as those that encode the transcription factors Bicoid and Nanos. Bicoid protein is expressed in a gradient that extends from the anterior end of the early embryo whereas Nanos protein is concentrated at the posterior end.
Fertilisation or fertilization (see spelling differences) also known as generative fertilisation syngamy and impregnation is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilization.
In developmental biology cleavage is the division of cells in the early embryo.The process follows fertilization with the transfer being triggered by the activation of a cyclin-dependent kinase complex. The zygotes of m…