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The archosaurian shift from larynx to syrinx must have conferred a selective advantage for crown birds, but the causes for this shift remain unknown. [10] To complicate matters, the syrinx falls into an unusual category of functional evolution: arising from ancestors with a larynx-based sound source, the syrinx contains significant functional overlap with the structure it replaced.
Adult neurogenesis in the avian brain occurs in many different pallial regions, including the song nuclei, the hippocampus, and the olfactory regions. [6] Even though adult neurogenesis is widespread across the telencephalon, all the regions where it is especially high are associated with the learning of new information, suggesting a possible function of adult neurogenesis to be offering an ...
The avian vocal organ is called the syrinx; [12] it is a bony structure at the bottom of the trachea (unlike the larynx at the top of the mammalian trachea). The syrinx and sometimes a surrounding air sac resonate to sound waves that are made by membranes past which the bird forces air.
This protein functions as a regulator at the early steps of DNA replication. It localizes in the cell nucleus during cell cycle phase G1, but translocates to the cytoplasm at the start of S phase. The subcellular translocation of this protein during the cell cycle is regulated through its phosphorylation by cyclin-dependent kinases .
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Cell changes in the cell cycle like the assembly of mitotic spindles and alignment of sister-chromatids along the spindles are induced by M cyclin- Cdk complexes. The destruction of M cyclins during metaphase and anaphase, after the Spindle Assembly Checkpoint is satisfied, causes the exit of mitosis and cytokinesis. [ 6 ]
As the eukaryotic cell cycle is a complex process, eukaryotes have evolved a network of regulatory proteins, known as the cell cycle control system, which monitors and dictates the progression of the cell through the cell cycle. [5]
Cdc25 is a dual-specificity phosphatase first isolated from the yeast Schizosaccharomyces pombe as a cell cycle defective mutant. [1] As with other cell cycle proteins or genes such as Cdc2 and Cdc4, the "cdc" in its name refers to "cell division cycle". [2] Dual-specificity phosphatases are considered a sub-class of protein tyrosine phosphatases.