BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 11 The Control of Gene Expression Modules 11.1 – 11.11

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Remove nucleus from egg cell Donor cell Add somatic cell from adult donor Grow in culture to produce an early embryo (blastocyst) Nucleus from donor cell Implant blastocyst in surrogate mother Remove embryonic stem cells from blastocyst and grow in culture Clone of donor is born (REPRODUCTIVE cloning) Induce stem cells to form specialized cells for THERAPEUTIC use

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In multicellular eukaryotes, cells become specialized as a zygote develops into a mature organism –Different types of cells make different kinds of proteins –Different combinations of genes are active in each type 11.2 Differentiation yields a variety of cell types, each expressing a different combination of genes CELLULAR DIFFERENTIATION AND THE CLONING OF EUKARYOTES

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Table 11.2

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most differentiated cells retain a complete set of genes –In general, all somatic cells of a multicellular organism have the same genes 11.3 Differentiated cells may retain all of their genetic potential

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –So a carrot plant can be grown from a single carrot cell Figure 11.3A Root of carrot plant Adult plant Root cells cultured in nutrient medium Cell division in culture Single cell Plantlet

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Early experiments in animal nuclear transplantation were performed on frogs –The cloning of tadpoles showed that the nuclei of differentiated animal cells retain their full genetic potential Figure 11.3B Tadpole (frog larva) Intestinal cell Frog egg cell Nucleus UV Nucleus destroyed Transplantation of nucleus Eight-cell embryo Tadpole

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The first mammalian clone, a sheep named Dolly, was produced in 1997 –Dolly provided further evidence for the developmental potential of cell nuclei Figure 11.3C

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Scientists clone farm animals with specific sets of desirable traits Piglet clones might someday provide a source of organs for human transplant 11.4 Connection: Reproductive cloning of nonhuman mammals has applications in basic research, agriculture, and medicine Figure 11.4

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Adult stem cells can also perpetuate themselves in culture and give rise to differentiated cells –But they are harder to culture than embryonic stem cells –They generally give rise to only a limited range of cell types, in contrast with embryonic stem cells 11.5 Connection: Because stem cells can both perpetuate themselves and give rise to differentiated cells, they have great therapeutic potential

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Differentiation of embryonic stem cells in culture Figure 11.5 Cultured embryonic stem cells Different culture conditions Different types of differentiated cells Heart muscle cells Nerve cells Liver cells

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A chromosome contains a DNA double helix wound around clusters of histone proteins DNA packing tends to block gene expression 11.6 DNA packing in eukaryotic chromosomes helps regulate gene expression GENE REGULATION IN EUKARYOTES

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.6 DNA double helix (2-nm diameter) Metaphase chromosome 700 nm Tight helical fiber (30-nm diameter) Nucleosome (10-nm diameter) Histones “Beads on a string” Supercoil (200-nm diameter)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An extreme example of DNA packing in interphase cells is X chromosome inactivation 11.7 In female mammals, one X chromosome is inactive in each cell Figure 11.7 EARLY EMBRYO Cell division and X chromosome inactivation X chromosomes Allele for orange fur Allele for black fur TWO CELL POPULATIONS IN ADULT Active X Inactive X Orange fur Inactive X Active X Black fur

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A variety of regulatory proteins interact with DNA and each other –These interactions turn the transcription of eukaryotic genes on or off 11.8 Complex assemblies of proteins control eukaryotic transcription Enhancers DNA Activator proteins Other proteins Transcription factors RNA polymerase Bending of DNA Transcription Promoter Gene Figure 11.8

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each stage of eukaryotic expression offers an opportunity for regulation –The process can be turned on or off, speeded up, or slowed down The most important control point is usually the start of transcription Review: Multiple mechanisms regulate gene expression in eukaryotes

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chromosome GENE RNA transcript mRNA in nucleus mRNA in cytoplasm Polypeptide ACTIVE PROTEIN GENE Exon Intron Tail Cap NUCLEUS Flow through nuclear envelope CYTOPLASM Breakdown of mRNA TranslationBroken- down mRNA Broken- down protein Cleavage/modification/ activation Breakdown of protein DNA unpacking Other changes to DNA TRANSCRIPTION Addition of cap and tail Splicing Figure 11.11