Biology · 2015 · May · Paper 2 · HL · TZ1 · Question paper

20EP01 [Personal identifier removed] Biology Higher level Paper 2 © International Baccalaureate Organization 2015 20 pages 2215 – 6008 Wednesday 6 May 2015 (morning) Instructions to candidates y Write your session number in the boxes above. y Do not open this examination paper until instructed to do so. y Section A: answer all questions. y Section B: answer two questions. y Write your answers in the boxes provided. y A calculator is required for this paper. y The maximum mark for this examination paper is [72 marks]. 2 hours 15 minutes – 2 – Section A Answer all questions. Write your answers in the boxes provided. 1. Diabetes is often associated with the failure of the β (beta) cells in the pancreas, but it is unclear what actually causes this failure. FoxO1 is a protein which acts as a transcription factor to regulate the expression of genes involved in cell growth. FoxO1 also regulates increase in number and differentiation in cells such as pancreatic β cells. A study was conducted using mice lacking the gene for FoxO1 in β cells (IKO) as well as normal (control) mice. Blood glucose levels after fasting were compared for four groups of mice: young (3 months old) male mice, young (3 months old) female mice, older females (who have had several pregnancies) and aging males (16–20 months). Blood glucose after fasting / mg ml–1 4 3 2 1 0 Key: Control IKO Mean 3 month old Older 3 month old Aging females females males males [Source: Chutima Talchai, Shouhong Xuan, Hua V. Lin, Lori Sussel, Domenico Accili, “Pancreatic β Cell Dedifferentiation as a Mechanism of Diabetic β Cell Failure”, Cell, Volume 150, Issue 6, 14 September 2012, Pages 1223–1234] (a) Compare blood glucose levels after fasting in young control mice and young IKO mice without FoxO1. [2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .