Question

1. A person has a mutation in their leptin gene, such that the leptin they make cannot bind to the leptin receptor. What do you predict about their weight/BMI? WHY?

2. A person has a mutation in their leptin receptor, such that it can bind to leptin, but then the receptor fails to activate. Will leptin be a viable treatment for this person? WHY?

3. Insulin binds to an insulin receptor on a cell. The receptor dimerizes and becomes phosphorylated on intracellular tails. Cytoplasmic kinases then become activated, then a glucose carrier is inserted into the cell membrane, and glucose enters the cell by facilitated diffusion. Label the different steps in this pathway: signal, reception, transduction, response

a. insulin ________________________

b. activation of cytoplasmic kinases _________________

c. insulin receptor phosphorylation____________________

d. glucose enters the cell _______________________

Answer 1

We know that leptin hormone is mainly responsible for the maintainance of the fat storage in the body and it also helps in the inhibition of hunger in the body. This hormone is mainly released by the adipocytes and it works in the arcuate nucleus of the hypothalamus Now about the mutation the Ob(lep) obesity leptin gene in case of the humans are located in the 7th chromosome and this gene code for a 16kda leptin protein that is about 167 amino acids long. When there is a mutation in this gene or a loss of function mutation this will result in extreme obesity in that person and his body weight will rise along with a sharp decrease in the Basal Metabolic Rate.

For a person whose leptin receptor has undergone a loss of function mutation and fails to activate administration of leptin will not be a viable treatment therapy because introduction of leptin will not cause any sort of change in the configuration or the functioning of receptor in this case and when it is inactivated by mutation it will still remain inactive even after the administration of leptin.

3a Insulin - SIGNAL

b activation of cytoplasmic kinases - RECEPTION

c receptor phosphorylation - TRANSDUCTION

d glucose enters the cell - RESPONSE