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16 - BIO 305 Problem set for lecture 16 Winter 2008 1...

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BIO 305 Problem set for lecture 16 Winter 2008. 1. Concept question. (C level) (A) In a single sentence, describe the conceptual relationship between the following trio of words. DNA lesion-cell division-mutation (B) Label the links on the concept map below. Draw and label at least one additional link. Examples of correct responses: (A) If a DNA lesion is not repaired prior to DNA synthesis and cell division, it will lead to incorporation of an incorrect base, hence mutation. (B) cancer – DNA repair: Loss of function mutations in DNA repair genes can lead to accumulation of mutations and eventually to cancer. Cancer – tumor suppressor gene: A loss of function mutation in tumor suppressor gene can contribute to cancer progression. Another example: Recessive mutations in tumor suppressor genes need to be homozygous before they can contribute to cancer progression. Cancer – oncogene: A gain-of-function mutation of an oncogene can contribute to cancer progression. Another example: Gain of function mutations in oncogenes which contribute to cancer progression tend to be dominant. DNA repair – tumor suppressor gene: Genes encoding proteins with DNA repair function are usually tumor suppressor genes. cancer Tumor suppressor gene oncogene DNA repair
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2. (B level) People with the genetic disease Xeroderma pigmentosum have a defect in repair of DNA that has been damaged by ultra-violet radiation. This disorder is caused by a recessive mutation on one of eight different genes that act together to repair the damaged DNA. Thus, the affected individuals accumulate mutations in somatic cells, especially after exposure to sunlight. Some of the mutations cause skin cancer. (a) Would the development of a person with Xeroderma pigmentosum be affected by his or her environment? Why? (b) An individual with Xeroderma pigmentosum has developed three skin cancers: one on the neck, one on left arm, one on the forehead. None of the cancers are malignant (i.e. they have not invaded other tissues). Would you
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