Question

The hormone melatonin regulates many physiological processes in vertebrates. Melatonin is synthesized by a gland in the brain, and it is carried by the bloodstream to different cells throughout the body. The effects of melatonin depend on the type of cell it is received by. Melatonin affects the process of bone remodeling, which renews the adult skeleton. This process is partly regulated by the actions of a type of bone cell called osteoblasts. The melatonin receptor, MT2, is a membrane protein found in cells such as osteoblasts. When the MT2 receptor is bound by melatonin, it directs a change in the activity of osteoblasts. A comparison of bone mass over six weeks in mice with functioning and non-functioning versions of the MT2 receptor revealed the following:MT2 ProteinIncrease in Bone Massnormal11.1%non-functioning8.3%Data courtesy of Sharan et al. 2017. Journal of Pineal Research Licensed under CC BY 4.0.Which of the following best explains the results?A. A mutation in the gene encoding MT2 disrupted the ability of some cells to respond to melatonin, but these changes did not affect the function of osteoblasts.В. Osteoblasts that have abnormalities in the structure of the MT2 protein did not respond to melatonin, and this impacted the function of the cell but did not have an effect on the organism.C. Osteoblasts that have abnormalities in the structure of the MT2 protein were more effective in synthesizing the melatonin needed to make new bone.D. A mutation in the gene encoding MT2 produced a non-functioning protein, which altered the function of a specialized cell and decreased the ability of the mice to produce new bone.

Answer 1

The data shows that the mice with non functioning MT2 receptors had a lower increase in bone mass after six weeks, which means their ability to respond to melatonin was affected, as well as the function of osteoblast.

This means D is the correct answer.