WA1 (Teacher) 2022 H1 Bio

Civics Group Index Number Name (use BLOCK LETTERS) ST ANDREW’S JUNIOR COLLEGE 2022 JC2 Weighted Assessment 1 H1 BIOLOGY 8876 STRUCTURED QUESTIONS 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, civics group and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagram, graph or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. All working for numerical answers must be shown. Conceptual error (C) Data Quoting (D) Expression (E) Misreading the question (Q) For Examiner’s Use STQ 1 /14 STQ 2 /12 Total /26 This document consists of 6 printed pages. [Turn over H1

QUESTION 1 BRCA 1 and BRCA2 are tumour suppressor genes which code for tumour suppressor proteins associated with DNA repair. Women with harmful mutations in either BRCA1 or BRCA2 are five times more likely to develop breast cancer and 10 - 30 times more likely to develop ovarian cancer than women without any BRCA mutations. Fig. 1.1 shows the progression of breast cancer. Fig. 1.1 (a) (i) Describe and explain how the multi-step process of cancer development relates to the information given as well as Fig 1.1. ……………………………………………………………………………………………… [6] 1 Accumulation of many mutations, including BRCA 1 and BRCA2 2 lead to excessive proliferation of the duct epithelial cells 3 Activation of telomerase gene enables cells to divide indefinitely. 4 Further mutations can lead to loss of contact inhibition /density-dependent inhibition which leads to tissue invasion. 5 Ref. Formation of benign tumour. 6 Loss of anchorage-dependent inhibition leads to metastasis/motility. 7 At this point, the tumour is considered malignant. (ii) Compare between cancerous breast duct epithelial cells and normal epithelial stem cells. ……………………………………………………………………………………………… [4] Similarities: 1 Both are unspecialised and undifferentiated. 2 Both can replicate indefinitely / both have telomerase activity.

Differences [any 2]: Cancerous epithelial cell Stem epithelial cell Ability to differentiate Do not differentiate into other cell types. Differentiate into duct epithelial cells. Cell division Undergo uncontrolled cell division. Undergo normal cell division. Anchorage- dependent inhibition Do not exhibit anchorage - dependent inhibition. /density-dependent /contact-dependent Exhibit anchorag e-dependent inhibition. /density-dependent /contact-dependent (b) Fig. 1.2 shows the various types of cells that are found in the human skin. Cells in the spinous layer, granular layer and stratum corneum provides a barrier protection against pathogens in the external environment. Stem cells in the basal layer will divide and differentiate into committed progenitors, which can only divide a limited num