In squirrels and chipmunks, as in humans, cholesterol is removed from the circulation, first by complexing with Low Density Lipoproteins (LDLs). Next, the cholesterol-LDL complex is bound to LDL receptors found predominantly on the surface of liver cells, which then undergo receptor-mediated endocytosis, thus removing the LDL-cholesterol from the blood serum. Inside the cells, a drop in pH causes the LDLs to separate from their receptors, and the receptors are ultimately returned to the cell surface via exocytosis. You are surprised to discover that in both squirrels and chipmunks, certain individuals are predisposed to suffering heart attacks at an early age, and these early heart attacks are linked to the presence of a mutation in the gene that codes for their LDL receptors. This is where the similarity ends. Some of the homozygous chipmunks have only the elevated LDL cholesterol levels and the defective receptors, others have elevated LDL-cholesterol, defective receptors, and numerous tumors on the legs and buttocks only, still other have some other combination of tumors, cholesterol deposits on the eyelids, tendonitis, and/or rings around the edge of the cornea. NAME and DEFINE the genetic phenomenon illustrated here.
In squirrels and chipmunks, as in humans, cholesterol is removed from the circulation, first by complexing with Low Density Lipoproteins (LDLs). Next, the cholesterol-LDL complex is bound to LDL receptors found predominantly on the surface of liver cells, which then undergo receptor-mediated endocytosis, thus removing the LDL-cholesterol from the blood serum. Inside the cells, a drop in pH causes the LDLs to separate from their receptors, and the receptors are ultimately returned to the cell surface via exocytosis.
You are surprised to discover that in both squirrels and chipmunks, certain individuals are predisposed to suffering heart attacks at an early age, and these early heart attacks are linked to the presence of a mutation in the gene that codes for their LDL receptors. This is where the similarity ends.
Some of the homozygous chipmunks have only the elevated LDL cholesterol levels and the defective receptors, others have elevated LDL-cholesterol, defective receptors, and numerous tumors on the legs and buttocks only, still other have some other combination of tumors, cholesterol deposits on the eyelids, tendonitis, and/or rings around the edge of the cornea. NAME and DEFINE the genetic phenomenon illustrated here.
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