The Control of Gene Expression Chapter 11 The Control of Gene Expression

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

Cloning has many benefits But evokes just as many concerns Cloning has many benefits But evokes just as many concerns

Gene Regulation-the turning on and off of genes 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.

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

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

Cell division in culture 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 of carrot plant Single cell Root cells cultured in nutrient medium Cell division in culture Figure 11.3 Plantlet Adult Plant

Two cell populations in adult 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 Early embryo Two cell populations in adult Cell division and random X chromosome inactivation Orange fur X chromosomes Active X Inactive X Inactive X Allele for orange fur Black fur Active X Allele for black fur Figure 11.5

11.10 Nuclear transplantation can be used to clone animals ANIMAL CLONING 11.10 Nuclear transplantation can be used to clone animals Nucleus from donor cell Donor cell Implant blastocyst in surrogate mother Clone of donor is born (reproductive cloning) Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo (blastocyst) Remove embryonic stem cells from blastocyst and grow in culture Induce stem cells to form specialized cells (therapeutic cloning) Figure 11.10

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

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

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 stem cells in bone marrow Nerve cells Cultured embryonic stem cells Heart muscle cells Different culture conditions Different types of differentiated cells Figure 11.12

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

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

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 Proto-oncogene DNA Mutation within the gene Multiple copies of the gene Gene moved to new DNA locus, under new controls Oncogene New promoter Hyperactive growth- stimulating protein in normal amount Normal growth- stimulating protein in excess Normal growth- stimulating protein in excess Figure 11.16A

Tumor-Suppressor Genes Tumor-Suppressor Genes Mutations that inactivate tumor suppressor genes Have similar effects as oncogenes Tumor-suppressor gene Mutated tumor-suppressor gene Normal growth- inhibiting protein Defective, nonfunctioning protein Cell division under control Cell division not under control Figure 11.16B

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

Colon cancer Develops in a stepwise fashion Colon cancer Develops in a stepwise fashion Colon wall 1 2 3 Cellular changes: Increased cell division Growth of polyp Growth of malignant tumor (carcinoma) DNA changes: Oncogene activated Tumor-suppressor gene inactivated Second tumor- suppressor gene inactivated Figure 11.18A

Accumulation of mutations Can lead to cancer Accumulation of mutations Can lead to cancer Chromosomes 1 2 3 4 mutation mutations mutations mutations Normal cell Malignant cell Figure 11.18B

11.20 Avoiding carcinogens can reduce the risk of cancer 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

Cancer in the United States Cancer in the United States Table 11.20