๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
D locus
D locus
The d locus, also known as the dilute locus (d), is located on chromosome 9 of the mouse genome and is associated with the myosin Va (Myo5a) gene. Mutations in this gene affect the clumping of melanin, thus reducing the overall absorbance of light and making the animalsโ color appear diluted. Melanin clumps in mice exhibiting this phenotype are much larger and more concentrated than those in black mice. These larger clumps decrease the surface area available for light absorbance by melanin. In practice, this can be seen microscopically whereby large clumps of melanin are found throughout the hair shaft. MYO5A is an actin-based motor protein that contains an N-terminal motor domain that binds to actin and a C-terminal domain that interacts with the melanosome through RAB27 (RAB27A, a member of the RAS oncogene family) and MLPH (melanophilin) (see Fig. 36.10). Actin-bound myosin Va functions to transport melanosomes to the cellโs periphery. The melanosomes are then transported to the melanocytes dendritic extensions where they are transferred to keratinocytes.12,45
Fig. 36.10 Ingenuity Pathway Analysis Softwareยฎ (http://www.ingenuity.com/) molecular pathway diagram for genes that interact in the coat color pathway. Many of the mutant mice in Fig. 36.9 have mutations in the genes in this pathway (red boxes). This illustrates how variations on a common trait, coat color, help to define a molecular pathway. It also illustrates the number of other genes involved with coat color not in this pathway, which will be future goals to integrate.