Q33 - Parabiosis Reveals a Circulating Satiety Hormone in Obese Mice

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Endocrine System Physiology Gene Interactions: Epistasis & Complementation Analysis

Sir Frederick Banting (1891-1941) and John Macleod (1876-1935) discovered insulin and invented modern diabetes treatment. This inspired similar investigations into body weight homeostasis and obesity: two mouse (Mus musculus) lines (obese; Ob, & diabetic; Db) have identical over-eating phenotypes. Each is deficient for a single, but different, gene. Damaging the arcuate nucleus in the brain, which is the structure soley responsible for regulating the sensation hunger, produces a similar phenotype. Mice were joined surgically, allowing a small amount of blood to flow between them, and then observed.

Figure for Q33: Parabiosis Reveals a Circulating Satiety Hormone in Obese Mice

Using the information and data, determine which of the statements are true or which are false.

A. Surgical connection allows mice to freely share nutrients.

B. Db mutants overproduce an appetite suppressing substance.

C. The products of genes Ob and Db act in the same pathway.

D. The WT product of gene Ob promotes a pathway which activates the arcuate nucleus.

E. Some cases of human obesity can be treated by administering a hormone.

← Previous: Q32 Next: Q34 →

Question reproduced from IBO 2017, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions