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DNA and RNA

DNA and RNA. Chapters 12 & 13. Hershey and Chase. Performed two experiments to show that DNA is genetic material . Worked with viruses to determine if it was the protein or the DNA that contained the genetic information. Experiment One.

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DNA and RNA

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  1. DNA and RNA Chapters 12 & 13

  2. Hershey and Chase • Performed two experiments to show that DNA is genetic material. • Worked with viruses to determine if it was the protein or the DNA that contained the genetic information.

  3. Experiment One • Bacteria were grown with a radioisotope of sulfur. The sulfur was used as a tracer. • Viruses (bacteriophages) were allowed to infect the bacterial cells. • Viral proteins were made within the host cell and contained the sulfur tracer.

  4. The viruses were then allowed to infect a group of bacteria without the tracers. • The colonies were spun in a blender to remove the viral protein coat. • There was no tracer in the fluid medium, but there was still tracer within the bacterial cells.

  5. Experiment Two • This was a repeat of experiment one, but phosphorous was added as a trace.

  6. Watson and Crick • Working with everything they knew about the chemical properties of DNA, they were able to construct a model of DNA out of wire and metal pieces.

  7. Parts of a nucleotide • 5-Carbon Sugar called deoxyribose (in DNA) or ribose (in RNA) • Phosphate Group • Nitrogenous Base – these are what make the nucleotides different.

  8. Purines are 2 ringed: Adenine or Guanine

  9. Pyrimidines are 1 ringed: Thymine or Cytosine

  10. Adenine binds to Thymine • Guanine binds to Cytosine • A purine will always bind to a pyrimidine to produce a base pair

  11. Two strands of nucleotides are held together by hydrogen bonds between bases. They coil to form a Double Helix.

  12. Replication of DNA occurs during the S-phase of Interphase • Proteins and enzymes (helicase) break the hydrogen bond between the bases causing the helix to unwind and expose the bases • Free Nucleotides (those within the nucleus) pair with the exposed bases with the help of DNA polymerase. • DNA Ligase (enzyme) ensures that all parts of the DNA strand are connected.

  13. 4. The DNA Strands will coil again creating two new identical strands. Result: Each strand will have one side from the original DNA and one side that is new.

  14. RNA • Single Strand – not a double helix • The four bases are different – adenine, cytosine, guanine, uracil • Adenine bonds to uracil • Guanine bonds to cytosine • RNA gets its code from the DNA code

  15. 3 types of RNA • Messenger (mRNA) – carries protein building instructions. Goes from the DNA in the nucleus to the ribosome • Ribosomal (rRNA) – makes up the ribosome • Transfer (tRNA) – delivers amino acids to the ribosomes. Has an anticodon specific to the amino acid.

  16. Protein Synthesis • Occurs in 2 processes: • Transcription – mRNA forms from DNA code in the nucleus and moves to the ribosome • Translation – tRNA matches its anticodon to the codons on mRNA creating an amino acid chain.

  17. Transcription • One gene on the DNA strand “unzips” and is copied with RNA bases • Transcription begins at a promoter – a sequence of bases that tells the RNA to begin binding. • When the DNA is transcribed, mRNA leaves the nucleus and goes to the ribosome for translation.

  18. Translation • mRNA is “translated” into a protein • mRNA arrives at the ribosome - 3 bases of mRNA = 1 codon (initiation) • tRNA comes to the ribosome and the anticodon matches to the codon on mRNA (elongation) • Amino Acids break off to form proteins (termination)

  19. Mutations • An inheritable change in genetic code, which may or may not cause a change in the proteins made.

  20. Deletion – one or more base pairs are removed from the DNA sequence • Example: A T G G C A C C G A T T T A A with deletion A T G G CG A T T T A A

  21. Insertion – one or more base pairs are inserted into the gene sequence • Example: A T G G C A C C G A T T T A A A T G G C C A C A C C G A T T T A A

  22. Base Pair Substitution - one or more base pairs are replaced with other base pairs • Example: A T G G C A C C G A T T T A A base pair substituted A T G G G G T C C G A T T T A A

  23. ghs.gresham.k12.or.us/.../chpt14/chpt14.htm • http://cnx.org/content/m12382/latest/dna.gif • http://www.chemsoc.org/ExemplarChem/entries/2003/imperial_Burgoine/replication.jpg • http://fig.cox.miami.edu/~cmallery/150/gene/c7.17.7b.transcription.jpg • http://sps.k12.ar.us/massengale/images/584ELONGATION3.gif • http://www.flyfishingdevon.co.uk/salmon/year3/psy339evolutionarypsychologyroots/watson-crick-dna.jpg • http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/pictures/hersheychase1953.jpg

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