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. You notice that one unique squirrel, which you have nicknamed “Tubby”, appears to be able to eat vast quantities of French fries, yet he seems incredibly healthy. Surprisingly, he is the son of two squirrels that were homozygous for the defective LDL receptor gene. 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.
You notice that one unique squirrel, which you have nicknamed “Tubby”, appears to be able to eat vast quantities of French fries, yet he seems incredibly healthy. Surprisingly, he is the son of two squirrels that were homozygous for the defective LDL receptor gene. NAME and DEFINE the genetic phenomenon illustrated here.
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