Name Section Question 2 Keratinocytes are the predominant cell type found in the epidermal layer and are named for their role as producers of the filamentous protein keratin, which helps to strengthen the skin Knowing that many of these cells die each day while an equal number are produced, you are interested in understanding where they come from and how the population is maintained a) You collect a sample of keratinocytes from a mouse epidermal layer and spread them on a plate in the proper media to allow them to grow. Though the cells are visibly indistinguishable from each other, you find that some fail to divide while others have formed large colonies. What might be different about the two types of cells? b) Yo all the cells from one of the large colonies, and grow them on a fresh plate. You see some of the cells again form large colonies, but most fail to divide. Explain these results c) You're curious about what distinguishes the large-colony forming cells from those that fail to divide. You suspect there might be a genetic difference First, you amplify many of the genes known to be involved in keratinocyte development from both populations and then you compare restriction digests of the DNA from large-colony forming cells to the DNA from non- dividing ones i)Do you expect the digests to be identical or different? Why? ii)To check for differences in what the cell populations are expressing, you build a CDNA library for each cell type. Do you expect these libraries to be identical or different? Why? 7012Fall2003Name:___________________________________ Section:_____ 7.012 Fall 2003 3 Question 2 Keratinocytes are the predominant cell type found in the epidermal layer and are named for their role as producers of the filamentous protein keratin, which helps to strengthen the skin. Knowing that many of these cells die each day while an equal number are produced, you are interested in understanding where they come from and how the population is maintained. a) You collect a sample of keratinocytes from a mouse epidermal layer and spread them on a plate in the proper media to allow them to grow. Though the cells are visibly indistinguishable from each other, you find that some fail to divide while others have formed large colonies. What might be different about the two types of cells? b) You take all the cells from one of the large colonies, and grow them on a fresh plate. You see some of the cells again form large colonies, but most fail to divide. Explain these results. c) You're curious about what distinguishes the large-colony forming cells from those that fail to divide. You suspect there might be a genetic difference. First, you amplify many of the genes known to be involved in keratinocyte development from both populations and then you compare restriction digests of the DNA from large-colony forming cells to the DNA from non￾dividing ones. i) Do you expect the digests to be identical or different? Why? ii) To check for differences in what the cell populations are expressing, you build a cDNA library for each cell type. Do you expect these libraries to be identical or different? Why?