I'm reading this article and it says the following:
"the PRL regulatory gene HoxA-11 experienced a period of strong positive selection in the stem-lineage of eutharian mammals"
What does this mean? I'm not to sure what they mean when they're referring to stem-lineage.
I will translate:
The PRL regulatory gene HoxA-11 experienced a period of selection during the early placenta development of mammals, such that successful reproduction was strongly favored by some variants of the gene, and others not favored for development. This positive selection for successful cell development resulted in the HoxA-11 regulation of female fertility and uterine development in mammals as we know it.
stem lineage: specialization of stem cells into specialized cells regulating growth.
Thank you so much! I really appreciate it!
When the article mentions the "stem-lineage of eutharian mammals", it is referring to an ancestral group of mammals that includes all living placentals (eutharian mammals) and their extinct relatives. In other words, it is talking about a common ancestor that gave rise to all present-day placental mammals.
To understand the concept of "stem-lineage" more clearly, it is helpful to be familiar with the idea of a phylogenetic tree. A phylogenetic tree is a diagram that illustrates the evolutionary relationships between different species or groups of organisms.
The stem-lineage is the part of the tree that connects the common ancestor to a specific group of organisms. In this case, the stem-lineage of eutharian mammals connects the common ancestor of all placental mammals to the various species that exist today. The stem-lineage can be thought of as the "stem" or base from which a particular group has branched out over time.
So when the article says that the PRL regulatory gene HoxA-11 experienced strong positive selection in the stem-lineage of eutharian mammals, it means that this specific gene had significant evolutionary changes and adaptations within the ancestral lineage leading to all placental mammals. This suggests that the gene played an important role in the evolution of placental mammals and likely contributed to their success and diversification.