Refer to the table.In mice, a single-gene mutation can lead to obesity.The Ob gene codes for the protein leptin.The recessive ob allele is a loss-of-function allele, so ob/ob mice do not produce leptin and they become obese.In an experiment, leptin was injected into ob/ob and Ob/Ob (wild-type) mice daily.The data in the table below were collected before the injections began (baseline) and 10 days later.(Assume that the Ob allele is dominant.) Researchers found that levels of the hormone leptin are high in the bloodstreams of most overweight humans.Based on the data in the table from the experiment on mice, what is a likely explanation for this observation in humans?
A) All the humans in the study were male.
B) The overweight individuals were ob/ob.
C) The overweight individuals were Ob/ob.
D) The leptin receptors in the overweight individuals had reduced sensitivity to leptin.
E) The individuals in the study lacked the leptin gene.

Question

Refer to the table.In mice, a single-gene mutation can lead to obesity.The Ob gene codes for the protein leptin.The recessive ob allele is a loss-of-function allele, so ob/ob mice do not produce leptin and they become obese.In an experiment, leptin was injected into ob/ob and Ob/Ob (wild-type) mice daily.The data in the table below were collected before the injections began (baseline) and 10 days later.(Assume that the Ob allele is dominant.)  Researchers found that levels of the hormone leptin are high in the bloodstreams of most overweight humans.Based on the data in the table from the experiment on mice, what is a likely explanation for this observation in humans?
A) All the humans in the study were male. 
B) The overweight individuals were ob/ob. 
C) The overweight individuals were Ob/ob. 
D) The leptin receptors in the overweight individuals had reduced sensitivity to leptin. 
E) The individuals in the study lacked the leptin gene.

Quizplus · Accepted Answer

The data in the table show that ob/ob mice (which do not produce leptin) have much higher levels of circulating leptin than Ob/Ob mice before and after the injections. This suggests that the ob/ob mice have a feedback loop in which the absence of leptin stimulates the production and release of more leptin. This feedback loop may also occur in overweight humans, leading to high levels of circulating leptin, but the leptin receptors in these individuals may have reduced sensitivity to leptin, leading to decreased effectiveness of the hormone in regulating appetite and metabolism.

Refer to the Table