Chap 12 DNA and RNA

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Chap 12 - DNA and RNA
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Chap 12-1 DNA

• Griffith and Transformation
• Combined dead disease-causing bacteria with live
  harmless bacteria
• Changed bacteria into disease-causing
• Some 'factor' was transferred from dead to live
  bacteria

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Avery and DNA

• Treated dead bacteria with enzymes that destroyed
  proteins, lipids, carbohydrates, and nucleic
  acids
• Determined that DNA was the 'transformation
  factor'

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Hershey-Chase Experiment

• labeled protein of one virus with 35S
• labeled DNA of other virus with 32P
• showed DNA entered bacteria, not protein
• DNA is hereditary material

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Structure of DNA

• DNA is polymer of nucleotides
• 1. 5-carbon sugar- deoxyribose
• 2. phosphate group
• 3. nitrogenous base
• -- purines - adenine, guanine
• -- pyrimidines - cytosine, thymine

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Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Phosphate group
Deoxyribose
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• DNA is a double stranded helix
• sugar-phosphate backbone
• bases in middle, with A--T and C--G

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Chap 12-2 DNA Replication

• DNA strand unzips - strands are complementary
• enzymes add nucleotides to both strands - DNA
  polymerase
• each new DNA molecule has one old and one new
  strand

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Base pairing

• Bases pair because of hydrogen bonding
• During replication and transcription, hydrogen
  bonds between base pairs are broken

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Chap 12-3 RNA and Protein Synthesis

• RNA - ribonucleic acid
• has ribose instead of deoxyribose
• has Uracil instead of Thymine
• single stranded

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3 Types of RNA

• mRNA - messenger RNA - long strand that carries
  copy of DNA
• tRNA - transfer RNA - short loop of RNA that
  carries amino acid to mRNA
• rRNA - ribosomal RNA - along with protein
  provides site for protein synthesis (ribosome)

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Transcription

• 1. mRNA is made from unzipped DNA
• RNA polymerase - enzyme that makes RNA
• 2. Promoters - regions of DNA that tell RNA
  polymerase where to start
• 3. mRNA is processed so that introns are removed
  and exons remain

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Genetic Code

• Codon - sequence of three nucleotides that code
  for ONE amino acid
• tRNA - has anti-codon on one end and amino acid
  on other

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Translation

• 1. ribosome attaches to mRNA near AUG start codon
• 2. tRNA carries amino acid and attaches to mRNA
• 3. second tRNA molecule attaches next to first
  tRNA

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• 4. -amino acids are joined
• -peptide chain passed to next tRNA
• -ribosome moves to next codon on mRNA
• 5. stop codon
• - ribosome falls off mRNA

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Chap 12-4 - Mutations

• Gene Mutations - changes in sequences of
  nucleotides
• 1. Frameshift mutation
• nucleotide is inserted or deleted
• can result in non-functional protein

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• 2. Point mutation
• change in single nucleotide/codon
• may or may not change the amino acid

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Chromosomal Mutations

• Breaks in chromosomes resulting in several
  different possibilities
• 1. Inversion -
• segment of chromosome gets turned around 180
  degrees

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• 2. Translocation -
• part of chromosome gets moved to another
  chromosome
• 3. Deletion -
• part of chromosome removed
• 4. Duplication -
• segment gets repeated

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Chap 12-5 Gene Regulation

• All cells have all genes
• Gene -
• regulatory sites
• promoter - where RNA polymerase binds to DNA
• nucleotide sequence

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• If a protein is not always needed, the gene for
  that protein is turned on and off at different
  times
• Proteins that bind to regulatory sites on DNA
  determine if gene is expressed

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• Operon - group of genes that operate together
• Repressor - protein that binds to DNA and blocks
  transcription

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Lac Operon

• Prokaryotes - bacteria
• Can use lactose as a food source
• Lac operon - genes that code for proteins
  (enzymes) that can break down lactose

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• No lactose present
• repressor binds to DNA
• transcription blocked
• Lactose present
• lactose binds to repressor, releases DNA
• genes are transcribed

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Eukaryotic gene regulation

• Cell specialization - cells differ because of
  which genes are expressed (eukaryotes)
• Gene regulation in eukaryotes is more complicated
  and allows for cell specialization

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Hox genes

• 'master control genes' in eukaryotes that
  control development
• determine organism's body plan