Chapter 1 Biology 102 Gene expression (cont.)/ Begin Cellular reproduction

Chapter 1 Lecture outline Gene expression and regulation (cont.) Gene expression and regulation (cont.) Mutations Mutations Regulation of gene expression Regulation of gene expression Cellular reproduction Cellular reproduction Types of cellular reproduction Types of cellular reproduction Mitosis vs. meiosis Mitosis vs. meiosis Overview of mitosis/cell cycle Overview of mitosis/cell cycle Steps of mitosis Steps of mitosis

Chapter 1 Mutations Mutations and protein synthesis Mutations and protein synthesis Source of mutations Source of mutations Exposure to mutagens Exposure to mutagens Errors in replication and transcription Errors in replication and transcription Results of mutation: Changes in DNA can result in changes in the proteins for which they code Results of mutation: Changes in DNA can result in changes in the proteins for which they code

Chapter 1 Examples of Mutations

Chapter 1 Effects of mutations Some are insignificant Some are insignificant More than one codon for most amino acids More than one codon for most amino acids Third nucleotide position is often not important Third nucleotide position is often not important G-U-n = valine G-U-n = valine U-C-n = serine U-C-n = serine C-G-n = arginine C-G-n = arginine Some are Harmful Some are Harmful Frameshift, missense or nonsense Frameshift, missense or nonsense

Chapter 1 Effects of mutations Mutations can be beneficial! Mutations can be beneficial! Altered proteins may be more effective than originals Altered proteins may be more effective than originals Mutations are the source of genetic variation Mutations are the source of genetic variation Significance to ability to evolve Significance to ability to evolveX-men!

Chapter 1 Gene expression Individual cells express only a small fraction of their genes Individual cells express only a small fraction of their genes Gene expression is influenced by developmental stage and environment Gene expression is influenced by developmental stage and environment How is gene expression regulated? How is gene expression regulated?

Chapter 1 Regulation of gene expression (cont.) Types of regulation Types of regulation Frequency of transcription Frequency of transcription Turned on or off at promotor region Turned on or off at promotor region Rate/amount of mRNA translated Rate/amount of mRNA translated Some mRNA stable, others break down Some mRNA stable, others break down Activation/inactivation of proteins Activation/inactivation of proteins Lifespan of the protein Lifespan of the protein

Chapter 1 Types of cell reproduction BinaryFission BinaryFission (bacteria) (bacteria) DNA replicated Membrane added

Chapter 1 False-Color EM of Dividing Bacterium Division plane Cell wall Cytoplasm Nuclear material

Chapter 1 Asexual reproduction by mitosis New individuals

Chapter 1 Asexual Reproduction by Mitosis

Chapter 1 Mitotic cell division Mitotic cell division & differ- entiation Functions of Mitosis in animals Tissues Organs Fertilized egg (zygote) Multicell stage

Chapter 1 Mitosis, Meiosis, and the Sexual Cycle

Chapter 1 telophase metaphase anaphase cell division G0: nondividing interphase Focus on Mitosis S: Synthesis of DNA; chromosomes duplicated S: Synthesis of DNA; chromosomes duplicated G 1 : Growth G 2 : Growth prophase cytokinesis Mitosis

Chapter 1 Interphase DNA exists as chromatin: The chromosomes (blue) are in the thin, extended state Wrapped around protein DNA is 2 meters long! Replicated while in this form The microtubules (red) extend outward from the nucleus to all parts of the cell.

Chapter 1 Prophase DNA condenses into distinct chromosomes DNA condenses into distinct chromosomes Additional winding Additional winding Relationship of genes and chromosomes Relationship of genes and chromosomes Diploid: Homologous pairs of chromosomes Diploid: Homologous pairs of chromosomes Sister chromatids held together by centromere at this stage Sister chromatids held together by centromere at this stage Don’t confuse diploid with sister chromatids! Don’t confuse diploid with sister chromatids! Mitotic spindle forms from microtubules Mitotic spindle forms from microtubules Chromosomes attached Chromosomes attached Nuclear membrane disappears Nuclear membrane disappears

Chapter 1 Metaphase Chromosomes are lined up in midline Chromosomes are lined up in midline The chromosomes have moved along the spindle microtubules Homologous chromosomes aligned “head to toe” At end of metaphase, centromeres release sister chromatids

Chapter 1 Anaphase Sister chromatids have separated, and one set of chromosomes moves along the spindle microtubule to each pole of the cell. Cell still diploid, but chromosomes now are only single chromatids Cell is always diploid throughout this process!

Chapter 1 Telophase The chromosomes have gathered into two clusters, one at the site of each future nucleus. Chromosomes begin to decondense back to chromatin Nuclear membrane forms Followed by cytokinesis Cytoskeleton “pinches” cell into two parts Plants form new cell wall

Chapter 1 Cytokinesis of a Ciliated Cell Cleavage Furrow Daughter Cells

Chapter 1 Cytokinesis in Plants Vesicles fuse to form cell wall and membranes Complete separation of daughter cells

Chapter 1 Mitosis: Review Kinetochores align at cell’s equator Nucleolus disappears; Nuclear envelope breaks down Microtubules attach to kinetochores Chromosomes condense and shorten Centrioles begin to move apart; Spindle forms Duplicated chromosomes remain elongated Centrioles have also been duplicated Late Interphase Early Prophase Late Prophase Metaphase

Chapter 1 Mitosis: Review (cont.) Free spindle fibers push poles apart Chromatids become independent chromosomes One set of chromosomes; Begin unwinding Nuclear envelope re- forms Cytoplasm divided along equator Each daughter gets 1 nucleus & half of cytoplasm Spindle disappears; Nucleolus reappears AnaphaseTelophase Cytokinesis Next Interphase

Chapter 1 How do cells “know” when to stop dividing? Cell senescence Cell senescence Cells are programmed to stop dividing. Cells are programmed to stop dividing. Cells of older people programmed to stop dividing earlier (50x for newborn cells, 30x for aged person's cells) Cells of older people programmed to stop dividing earlier (50x for newborn cells, 30x for aged person's cells) Growth control Growth control Cell division inhibited by contact with other "like" cells. Cell division inhibited by contact with other "like" cells. Ex: wound closure. Ex: wound closure. Cancer cells do not exhibit growth control. Something has gone haywire. They keep growing. Cancer cells do not exhibit growth control. Something has gone haywire. They keep growing.