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THE GENETIC MATERIAL

THE GENETIC MATERIAL. Chapter 6. Properties Of Genetic Material. Repository of genetic information Info must be accessible, allow cell to respond Info must be in form transmissible to progeny Physical and chemical stability Potential for heritable change. Repository of Genetic Information.

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THE GENETIC MATERIAL

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  1. THE GENETIC MATERIAL Chapter 6

  2. Properties Of Genetic Material • Repository of genetic information • Info must be accessible, allow cell to respond • Info must be in form transmissible to progeny • Physical and chemical stability • Potential for heritable change

  3. Repository of Genetic Information • Types of information to be conveyed • Sequence of all RNAs • Protein sequences • Signals • Start and stop for RNA pol • RNA processing sites • Translation start and stop signals • Replication start and stop sites • Signals that affect topography of chromosomes (centromeres, telomeres, spacers, etc.)

  4. Transmission of Information • Faithful replication necessary • RNA short-lived, DNA persists Pyrimidine:purine pairing maintains consistent width, mismatches easily detected • Complementary copies allow quick recognition of mistakes

  5. Physical and Chemical Stability • Double–stranded structure provides some protection from chemical attack • Hydrophobic core bases less subject to hydrolysis Groups involved in base pairing are protected by a hydrophobic barrier.

  6. Physical and Chemical Stability • Bases generally stable • One major exception: Cytosine • EX Deamination of Cytosine H-O-H NH3 RULE: If you see uracil in DNA, cut it out

  7. Limited Ability to Change-Mutations • Mutation—the only source of new alleles • A change in the base sequence of DNA • Ability of a species to adapt lies in the diversity of its alleles • though stability necessary, must have some limited ability to generate new alleles while preserving parent line

  8. Mutagenesis • Chemical alteration of base that gives it new H-bonding properties • different base incorporated in complementary strand • Replication errors • Misincorporation • Extra base • Deletion

  9. Mutations • Transition----Purine replaced by purine, pyrimidine by pyrimidine • Transversion---Pyr replaced with pur, pur replaced with pyr. • Double stranded nature of DNA—a safeguard in case the mutation doesn’t work

  10. RNA as Genetic Material • DNA not only genetic material • RNA sometimes used by viruses • Considerations • Viruses lack active cytoplasm • Produce huge # of progeny

  11. Retrovirus Structure

  12. Deamination of Cytosine and 5-methylcytosine -------------------------------------------------------------------------------

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