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The Control of Gene Expression: To Clone or Not to Clone?

This chapter explores gene regulation, differentiation of cells, X chromosome inactivation, animal cloning, and the ethical concerns surrounding human reproductive cloning. It also discusses therapeutic cloning and the genetic basis of cancer.

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The Control of Gene Expression: To Clone or Not to Clone?

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  1. 0 Chapter 11 The Control of Gene Expression

  2. 0 To Clone or Not to Clone? A clone is an individual created by asexual reproduction And thus is genetically identical to a single parent

  3. 0 Cloning has many benefits But evokes just as many concerns

  4. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes. Gene Regulation-the turning on and off of genes Can help organisms respond to environmental changes. Gene expression-the process by which genetic information flows from genes to proteins; from genotype to phenotype.

  5. 0 11.2 Differentiation yields a variety of cell types, each expressing a different combination of genes In multicellular eukaryotes Cells become specialized as a zygote develops into a mature organism

  6. 0 Different types of cells Make different proteins because different combinations of genes are active in each type Muscle cell Pancreas cells Blood cells Figure 11.2

  7. 0 11.3 Differentiated cells may retain all of their genetic potential Most differentiated cells Retain a complete set of genes Regeneration-the regrowth of lost body parts Root ofcarrot plant Single cell Root cells culturedin nutrient medium Cell divisionin culture Figure 11.3 Plantlet Adult Plant

  8. 0 11.5 In female mammals, one X chromosome is inactive in each cell An extreme example of DNA packing in interphase cells Is X chromosome inactivation in the cells of female mammals Two cell populationsin adult Early embryo Cell divisionand randomX chromosomeinactivation Orangefur Active X X chromosomes Inactive X Inactive X Black fur Allele fororange fur Active X Allele forblack fur Figure 11.5

  9. 0 ANIMAL CLONING Nucleus fromdonor cell Donorcell Clone of donor is born (reproductive cloning) Implant blastocyst insurrogate mother 11.10 Nuclear transplantation can be used to clone animals Grow in culture to produce an early embryo (blastocyst) Add somatic cell from adult donor Remove nucleusfrom egg cell Remove embryonic stemcells from blastocyst andgrow in culture Induce stem cells toform specialized cells(therapeutic cloning) Figure 11.10

  10. 0 CONNECTION 11.11 Reproductive cloning has valuable applications, but human reproductive cloning raises ethical issues Reproductive cloning of nonhuman mammals Is useful in research, agriculture, and medicine Figure 11.11

  11. 0 Critics point out that there are many obstacles Both practical and ethical, to human cloning

  12. 0 CONNECTION 11.12 Therapeutic cloning can produce stem cells with great medical potential Like embryonic stem cells, adult stem cells Can perpetuate themselves in culture and give rise to differentiated cells Blood cells Adult stemcells in bone marrow Nerve cells Culturedembryonicstem cells Heart muscle cells Different cultureconditions Different types ofdifferentiated cells Figure 11.12

  13. 0 Unlike embryonic stem cells Adult stem cells normally give rise to only a limited range of cell types

  14. 0 THE GENETIC BASIS OF CANCER 11.16 Cancer results from mutations in genes that control cell division Cancer cells, which divide uncontrollably Result from mutations in genes whose protein products affect the cell cycle

  15. 0 Proto-oncogene DNA Proto-Oncogenes A mutation can change a proto-oncogene (a normal gene that promotes cell division) Into an oncogene, which causes cells to divide excessively Gene moved tonew DNA locus,under new controls Mutation withinthe gene Multiple copiesof the gene New promoter Oncogene Normal growth-stimulatingproteinin excess Normal growth-stimulatingproteinin excess Hyperactivegrowth-stimulatingprotein innormalamount Figure 11.16A

  16. 0 Mutated tumor-suppressor gene Tumor-suppressor gene Tumor-Suppressor Genes Mutations that inactivate tumor suppressor genes Have similar effects as oncogenes Normalgrowth-inhibitingprotein Defective,nonfunctioningprotein Cell division notunder control Cell divisionunder control Figure 11.16B

  17. 0 11.18 Multiple genetic changes underlie the development of cancer Cancers result from a series of genetic changes in a cell lineage

  18. 0 Colon wall Colon cancer Develops in a stepwise fashion 2 1 3 Cellularchanges: Increasedcell division Growth of polyp Growth of malignanttumor (carcinoma) Tumor-suppressorgene inactivated Second tumor-suppressor geneinactivated DNAchanges: Oncogeneactivated Figure 11.18A

  19. 0 Chromosomes 1 2 4 3 mutations mutation mutations mutations Accumulation of mutations Can lead to cancer Normalcell Malignantcell Figure 11.18B

  20. 0 CONNECTION 11.20 Avoiding carcinogens can reduce the risk of cancer Reducing exposure to carcinogens (which induce cancer-causing mutations) And making other lifestyle choices can help reduce cancer risk

  21. 0 Cancer in the United States Table 11.20

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