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 10 Molecular Biology of the Gene Modules – 10.22

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings VIRUSES: GENES IN PACKAGES Viral DNA may become part of the host chromosome Phage New phage DNA and proteins are synthesized Phage DNA inserts into the bacterial chromosome by recombination Attaches to cell Phage DNA Bacterial chromosome Phage injects DNA Occasionally a prophage may leave the bacterial chromosome Many cell divisions Lysogenic bacterium reproduces normally, replicating the prophage at each cell division Prophage Phage DNA circularizes LYSOGENIC CYCLE Cell lyses, releasing phages Phages assemble LYTIC CYCLE OR

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Many viruses have RNA, rather than DNA, as their genetic material –Example: flu viruses Connection: Many viruses cause disease in animals Figure 10.18A Membranous envelope RNA Protein coat Glycoprotein spike

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some animal viruses steal a bit of the host cell’s membrane Figure 10.18B VIRUS Glycoprotein spike Protein coat Envelope Viral RNA (genome) 1 Plasma membrane of host cell Entry 2 Uncoating Viral RNA (genome) 3 RNA synthesis by viral enzyme 4 Protein synthesis 5 RNA synthesis (other strand) mRNA New viral protein New viral proteins 6 Assembly 7 Exit Template New viral genome

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most plant viruses have RNA –Example: tobacco mosaic disease Connection: Plant viruses are serious agricultural pests Figure ProteinRNA

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The deadly Ebola virus causes hemorrhagic fever –Each virus is an enveloped thread of protein-coated RNA Hantavirus is another enveloped RNA virus Connection: Emerging viruses threaten human health Figure 10.20A, B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings HIV is a retrovirus The AIDS virus makes DNA on an RNA template Figure 10.21A Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Inside a cell, HIV uses its RNA as a template for making DNA to insert into the host chromosome Figure 10.21B Viral RNA DNA strand Double- stranded DNA Viral RNA and proteins CYTOPLASM NUCLEUS Chromosomal DNA Provirus DNA RNA

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Virus studies help establish molecular genetics Molecular genetics helps us understand viruses –such as HIV, seen here attacking a white blood cell Virus research and molecular genetics are intertwined Figure 10.22