Well, you would use Punnet squares. Don't forget that heterozygous means that the alleles are different so Rr. Homozygous means that the genotype will have the same genes rr. When you put together the Punnet squares, I always like to determine the percentage of phenotypes possible. In this case 50% of them are going to be white, and 50% of them are going to be red.
The negative feedback principle in human physiology is involved in this case. The inciting factor here is the increase in blood glucose that will be recognized by the pancreatic islet cells (the endocrine part of the pancreas) and will signal insulin release. Insulin upregulates glucose transporter proteins in cells, especially muscle cells, which will then stimulate glucose uptake from blood. Insulin also stimulates glycogen formation in the liver. These events will subsequently lower blood glucose and low blood glucose will now inhibit the insulin secretion by the pancreas. In the event of hypoglycemia or dangerously low blood glucose, the first adaptive mechanism of the body is to produce glucagon from the pancreatic islet cells. Glucagon will stimulate glycogen breakdown in the liver and therefore raise blood glucose levels to normal.<span> </span>
