© 2003 Mark S. Davis Chapter 21 Nucleic Acids

© 2003 Mark S. Davis Queen Victoria Hemophilia

© 2003 Mark S. Davis Goals Describe nucleotides, RNA and DNA, polypeptides Know the 3D structure of nucleic acids Describe mutations and their effects Describe viruses and Recombinant DNA technology

© 2003 Mark S. Davis Chromosomes Humans have 46 – Germ cells have 23 – – Contain all genetic information of the organism

© 2003 Mark S. Davis RNA Leave nucleus

© 2003 Mark S. Davis Nucleotides Monomers that make up DNA and RNA

© 2003 Mark S. Davis Nucleotides Made from –

© 2003 Mark S. Davis Naming Sugar and base –Adenine + sugar = –Cytosine + sugar = is second part of the name dGMP

© 2003 Mark S. Davis 5’ – 3’ Phosphodiester In making DNA – This is the direction used for naming

© 2003 Mark S. Davis DNA Structure Watson and Crick 1953 Complementary pairs –

© 2003 Mark S. Davis Complementary Strands Bases located Maximum Hydrophobic bonds to the bases above and below

© 2003 Mark S. Davis Given… G A T T A C A What is the complementary strand?

© 2003 Mark S. Davis Size of DNA 3x10 9 base pairs Organized around Around 200 base pairs/

© 2003 Mark S. Davis RNA Single strand Different types –

© 2003 Mark S. Davis RNA Pairing Only about ½ molecules base pair Acceptor stem: Anticodon -

© 2003 Mark S. Davis Information flow Replication: Transcription: Translation:

© 2003 Mark S. Davis Replication Copy all 46 chromosomes in less than a day (about 8 hrs) Error – Always in 5’  3’ direction and two strands grow opposite DNA

© 2003 Mark S. Davis DNA Polymerase “Checks” the accuracy of the pairing and correcting errors

© 2003 Mark S. Davis Practice What is the corresponding daughter strand to the parent –

© 2003 Mark S. Davis Transcription Transcription bubble RNA Polymerase acts on the template strand only There is a start site There is a termination site

© 2003 Mark S. Davis RNA Polymerase No proofreading function Error Initial RNA is called primary transcript RNA, ptRNA Later modified to the other types

© 2003 Mark S. Davis What RNA is formed? If the DNA sequence is: What is the RNA that is synthesized?

© 2003 Mark S. Davis Post transcription End capping – Base modification Splicing –

© 2003 Mark S. Davis Translation Protein synthesis – – Sequence of bases specifies amino acid sequence – 64 codons for 20 amino acids –

© 2003 Mark S. Davis Translation Each tRNA carries ONLY ONE aa Aminoacyl-tRNA synthetase – Peptidyl transferase – Synthesis terminates when STOP codon is reached

© 2003 Mark S. Davis Posttranslational Processing Most lose Folding begins Disulfide-bridging Quaternary structures assembled

© 2003 Mark S. Davis Control at every step Not every cell expresses every gene Specialized Repressor proteins – Inducer proteins –

© 2003 Mark S. Davis Mutations Error in base sequence – – – Substitution (point) mutations – Frameshift mutations –

© 2003 Mark S. Davis Spontaneous Mutations and Mutagens Spontaneous mutations – Sodium nitrite –In processed meats –Converts cytosine to uracil –Overall danger thought to be low –Reduces occurrence of botulism

© 2003 Mark S. Davis Spontaneous Mutations and Mutagens Benzopyrene – –Found in car exhaust, tobacco smoke, burnt meats Radiation –

© 2003 Mark S. Davis Silent Mutations Base-sequence errors that don’t affect organism –64 codons for 20 amino acids – –Change may be in unimportant region – –Genes have 2 or more copies

© 2003 Mark S. Davis Mutations Somatic cells – Germ cells – –

© 2003 Mark S. Davis Antibiotics Chemicals to fight infection Block protein synthesis – – Must finish whole course Bacteria Antibiotic resistant bacteria

© 2003 Mark S. Davis Viruses DNA or RNA with protein coat No functions outside cell Enter cell and “hijack” it Each virus attacks only specific cells –TMV –AIDS

© 2003 Mark S. Davis DNA Viruses Enter host cell and nucleus Insert themselves into Hiding inside cell – hard for immune system to detect Can stay indefinitely

© 2003 Mark S. Davis RNA Viruses Enters cell Directs synthesis of Uses machinery of host to make copies of itself

© 2003 Mark S. Davis Retroviruses Special RNA virus Enters cell and directs synthesis of viral DNA using reverse transcriptase DNA inserts into host genome Can hide or remain dormant for long periods of time –HIV

© 2003 Mark S. Davis Treatment Antibiotics don’t work Body doesn’t recognize virus once hiding in host cell Best method:

© 2003 Mark S. Davis Recombinant DNA Technology Began in mid-70s Transplanting or altering of DNA Benefits –Therapeutic drugs –Improvements to crops and herds –Curing/treating of genetic diseases

© 2003 Mark S. Davis Production of human insulin First application of recombinant DNA technology Uses yeast and bacteria as vehicle –Bacteria have genomic DNA and a plasmid Less side effects than cow or pig insulin

© 2003 Mark S. Davis Process Identify gene encoding wanted protein 1.Isolate this gene from the donor DNA 2.Splice into plasmid (vector DNA) 1.Restriction enzymes 3.Recombinant DNA (new plasmid) back into E. coli 1.Chemical shock 2.Heat shock

© 2003 Mark S. Davis Other techniques Microinjections –Direct injection of DNA into nucleus of another cell –Cloning ~~~ Dolly Viral vectors –Altered virus (usually retrovirus) –Carries new DNA to host cell –Research now for cystic fibrosis

© 2003 Mark S. Davis A Little More About Cloning Enucleation of cell: – whatiscloning/images/enucleation.mpghttp://gslc.genetics.utah.edu/units/cloning/ whatiscloning/images/enucleation.mpg Nuclear Transfer: – whatiscloning/images/transfer.mpghttp://gslc.genetics.utah.edu/units/cloning/ whatiscloning/images/transfer.mpg Cloning “Practice”: – lickandclone/ lickandclone/

© 2003 Mark S. Davis Transgenic Breeding Organisms with altered DNA Grow faster, larger, etc. Resistant to pests – transgen.htmlhttp:// transgen.html Many already in your supermarket

© 2003 Mark S. Davis Gene Therapy Human Genome Project –Finished with sequence –Now identify genes and proteins Insert correct gene for defective one Modified adenovirus (common cold) –Aerosol spray inhaled –Injection into bloodstream –Incubation of cells

© 2003 Mark S. Davis Ethical Considerations Effects of recombinant DNA? Can we test people for diseases? –Alzheimer’s; Huntington’s Gene Therapy –Enhance intelligence, strength –Pick eye color Who will benefit? Will anyone suffer?

© 2003 Mark S. Davis Internet Sites of Interest PBS Site about GMOs – Genetic Science Learning Center – NWABR –