How are maternal effect genes related to egg-polarity genes? Maternal effect genes provide the necessary factors and molecular cues that guide the localization and expression of egg polarity genes, ensuring the establishment of polarity and proper patterning.
Embryonic development is the process by which a single fertilized egg or zygote undergoes a series of intricate and highly regulated changes to develop into a multicellular organism. It involves numerous cellular and molecular events that shape the structure and function of the developing embryo. Moreover, maternal effect genes and egg polarity genes are two types of genes important in embryonic development.
Key Areas Covered
1. What are Maternal Effect Genes and Egg-polarity Genes
– Definition, Function, Features
2. How are Maternal Effect Genes Related to Egg-polarity Genes
– Interaction Between Maternal Effect Genes and Egg-polarity Genes
Maternal Effect Genes, Egg-polarity Genes
What are Maternal Effect Genes and Egg-polarity Genes
Maternal effect genes are genes one inherits from the mother. These control the expression of other genes in the developing embryo. Meanwhile, egg polarity genes are responsible for determining the egg’s and embryo’s orientation and polarity.
Maternal genes are transcribed and translated in the mother’s germ cells; their gene products, such as mRNA and proteins, are deposited into the egg during oogenesis. These maternally derived factors are essential in early embryonic development before zygotic gene activation occurs. Therefore, maternal effect genes can control the expression of downstream genes by providing regulatory molecules that establish concentration gradients or by acting as transcription factors themselves.
Egg polarity genes are responsible for establishing the polarity and axes of the egg and the resulting embryo. They determine the distribution and localization of key molecules that define different regions of the developing embryo. Moreover, egg polarity genes code for cytoplasmic factors or localized determinants that are asymmetrically distributed within the egg, essential for establishing the initial AP axis. They also help in influencing the cell fate decisions during development.
How are Maternal Effect Genes Related to Egg-polarity Genes
Maternal effect genes are responsible for the synthesis, localization, and proper distribution of the proteins and mRNA molecules encoded by egg polarity genes. Maternal effect genes act upstream of egg polarity genes by controlling their expression or regulating the transport and localization of their products. The initial polarity of the egg is established by the interaction between these two classes of genes. This interaction also ensures proper patterning during embryogenesis.
One can observe the interaction between maternal effect genes and egg polarity genes in Drosophila melanogaster or fruit fly. Maternal effect genes such as bicoid and nanos are useful in establishing the AP axis in the early Drosophila embryo. The bicoid gene encodes a transcription factor that is localized to the anterior end of the developing egg. High levels of bicoid mRNA at the anterior end of the embryo lead to the expression of specific downstream target genes that specify anterior cell fates.
The nanos mRNA is localized to the posterior end of the Drosophila embryo. Moreover, nanos protein produced from nanos mRNA acts as a repressor of anterior-specific genes. This effectively restricts their expression to the anterior region. Furthermore, a sharp boundary is created between the anterior and posterior domains of the embryo, establishing the AP axis.
These interactions between the bicoid and nanos demonstrate how maternal effect genes control the expression and localization of egg polarity genes to establish the AP axis. Moreover, bicoids and nanos provide positional information to the developing embryo. In addition, the concentration gradients established by these genes serve as cues for the subsequent cell fate determination along the AP axis.
In summary, maternal effect genes and egg polarity genes are intricately linked in their roles during early embryonic development. The maternal-effect genes control the expression and localization of egg polarity genes, allowing for the establishment of polarity and proper patterning. Therefore, the interaction between these two classes of genes is essential for the specification of the cell fates along the AP axis.
1. “Maternal effect crosses1.svg – From Wikimedia Commons, the free media repository” By Celefin – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Maternal effect mRNAs-2” – created with Adobe Illustrator. (CC BY-SA 4.0) via Commons Wikimedia