Case study (4 Marks)

Question 14 Marks

Read the following text carefully and answer the questions that follow:
Cancer refers to any one of a large number of diseases characterized by the development of abnormal cells that divide uncontrollably and have the ability to infiltrate and destroy normal body tissue. Cancer often has the ability to spread throughout your body. Cancer is the second-leading cause of death in the world.

i. How does a cancerous cell differ from a normal cell? (1)
ii. Benign tumor is less dangerous than malignant tumor. Why? (1)
iii. Describe causes of cancer. (2)
OR
Mention two methods of treatment of the disease. (2)

Answer

i. In normal cells, growth and differentiation are highly controlled and regulated (contact inhibition). The cancerous cells have lost the property of contact inhibition, hence continue to divide giving rise to masses of cells (tumors).
ii. The benign tumor remains confined in the organ affected as it is enclosed in a connective tissue sheath and does not enter the
metastatic stage.
iii. Cancer may be caused due to carcinogens which are physical (X-rays, gamma rays and UV rays), chemicals (Nicotine,
Aflatoxin, Cadmium oxide, Asbestos) and biological (viral oncogenes and proto-oncogenes).
OR
Surgery, radiotherapy, Chemotherapy, immunotherapy by using biological response modifiers like a-interferons.

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Question 24 Marks

Read the following text carefully and answer the questions that follow:
The reproductive cycle in female primates (e.g. monkeys, apes and human beings) is called the menstrual cycle. In human females, menstruation is repeated at an average interval of about 28/29 days, and the cycle of events starting from one menstruation till the next one is called the menstrual cycle Anita has show Diagrammatic presentation of various events during a menstrual cycle.

i. What role do pituitary gonadotropins play during the follicular and ovulatory phases of the menstrual cycle? (1)
ii. The first half of the menstrual cycle is called the proliferative phase as well as the follicular phase. Give reason.(2)
iii. Why does corpus luteum stay active throughout pregnancy and in the absence of fertilization, is active only for 10-12 days?
OR
What happens to corpus luteum in human female if the ovum is (2)
a. fertilised,
b. not fertilised?

Answer

i. Gonadotropin-releasing hormone (GnRH) also called gonadotropin-releasing factor (GnRH) is secreted by the hypothalamus of the brain, which stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH stimulates the ovarian follicles to produce estrogens during the proliferative phase. LH stimulates the corpus luteum of the ovary to secrete progesterone.
ii. The first half of the menstrual cycle is called the follicular phase because estrogens secreted by the cells of maturing Graafian follicles control the changes in the secondary sex organs. It is also called the proliferative phase because the growth and proliferation of tissue on the wall of the uterus, vagina take place.
iii. During the luteal phase, the leftover parts of Graafian follicle transform into the corpus luteum. It discharges large quantities of progesterone hormone which is required for the maintenance of the endometrium. The endometrium is important for implantation of the fertilized egg and various other stages of pregnancy. Hence, corpus luteum has a long life in pregnancy. In the absence of fertilization, upholding of the corpus luteum is not required and thus it declines within 10-12 days, which
causes the lining of the endometrium to menstruate and hence the onset of the new menstrual cycle.
OR
i. In case of fertilisation, the corpus luteum continues secreting progesterone which is required for the maintenance of endometrium during pregnancy.
ii. In the absence of fertilisation, the corpus luteum degenerates and gets converted into corpus albicans. Deficiency of progesterone causes disintegration of the endometrium leading to menstruation and thus, a new cycle starts.

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Biology Case study (4 Marks)

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