2016 VJC H2 Biology Prelims Paper 2 Answers

1    VICTORIA JUNIOR COLLEGE BIOLOGY DEPARTMENT JC2 PRELIMINARY EXAMINATIONS 2017 HIGHER 2 9744/2 Propose answers 1 Fig.1 shows an electron micrograph of an organelle. There are two distinct group of vesicles (Boxes B and C) associated with this organelle. Fig. 1 (a) (i) Identify organelle A. Feature Golgi body/ golgi apparatus;; A stack of membranes with swollen ends;; (ii) Describe the differences in the role of the vesicles that fuse with the forming face and the vesicles that are formed at the maturing face. [4]  Box C: [2m]  vesicles contain proteins and/or lipids;  transported from rER and sER;  that will undergo chemical modification within the golgi body;  examples of modification: glycolysation, phosphorylation etc  Box B: [2m]  Packaging and transport fn: Vesicles containing modified products will be transported to the cell membrane;  where they fuse and release the products to the outside of the cell/via exocytosis; (b) Suggest how the lack of E3A expression can lead to a disruption in the structure and function of the Organelle A.  Lack of gene expression means that the enzyme E3A is not produced/ transcribed and translated;;  Proteins that are tagged by ubiquitin, are meant for degradation;;

2     These proteins are either damaged/abnormal/excess;;  Removal of these proteins help to maintain the normal functions of the GA (idea of);; (A: reverse argument) (c) State two characteristics, one in structur e and one in chemical property that you would expect to see in ubiquitin protein ligase. [2] Structure: globular / specific 3D configuartion Chemical ppty: solubility in water;;   2 (a) Explain the similarity in the pattern seen in both HDAC mRNA and HDAC protein. [2]  HDAC mRNA is the template for the translation /synthesis of HDAC protein;;  Decrease in mRNA concentration lead to a decrease in concentration of HDAC protein;; (b) (i) What information about the gene expression of RUNX3 can one conclude from the data at the beginning of the experiment? Explain your answer. [3] There are 2 possible answers to this question. Possible answer 1  RUNX3 gene is silenced/ down regulated;; (Note: this last mark is only awarded if student’s answer shows that there is an attempt to link RUNX3 gene expression to HDAC levels shown in Fig 2.1)  How does HDAC down regulate RUNX3 expression:  Remove acetyl groups from lysine residues of histones;  Increase positive charge of histones;  Results in negatively RUNX3 gene being more tightly coiled around histones;  Promoter less accessible to transcription factors and RNA polymerase;  Data: Highest HDAC mRNA and protein; Possible answer 2  RUNX3 gene is upregulated;; (Note: this last mark is only awarded if student’s answer shows that there is an attempt to link RUNX3 gene expression to HDAC levels shown in Fig 2.1)  How does RUNX3 upregulate HDA  RUNX3 TF binds to promoter of HDA