DNA and Genes

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DNA and Genes

• (Chapter 11.1)

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? History of DNA

• 1800s Mendel determined that offspring inherited
  traits from parents
• 1944 Biomolecule that was involved with heredity
  was DNA (originally proteins were thought to pass
  on traits because DNA was too simple)

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• Rosalind Franklin and Maurice Wilkins took
  diffracted photographs of DNA
• X-rays were passed through DNA crystals, the
  X-rays were bent by the atoms in the DNA molecule
  producing an image of the shape

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• 1953 Watson Crick developed a model of DNA
  using the diffraction photographs
• Double Helix DNA comes in 2 long strands that
  wrap around each other, spiral staircase

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? Why is DNA so important?

• DNA is known as blueprint of life
• DNA contains instructions for making proteins
  within the cell
• Genes are on our chromosomes, chromosomes are
  made of DNA

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• Important for all life on Earth, makes each
  individual plant or animal unique
• Helps us understand diseases better find
  potential cures
• Better food crops

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? DNA Nucleotides

• DNA is a nucleic acid made from subunits called
  nucleotides
• Nucleotide 3 parts five-carbon sugar,
  phosphate group, nitrogenous base
• Deoxyribose the sugar in a DNA nucleotide

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? How the Double Helix stays together
phosphates

• Double Helix has two strands that twist together
• One strand of DNA is like one half of a zipper
• The backbone of the molecule is alternating
  phosphates and deoxyribose sugar
• The teeth are nitrogenous bases

deoxyribose
bases
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• One strand of DNA (half of a zipper) is a polymer
  of nucleotides
• One strand of DNA has millions of nucleotides

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? Nitrogenous (Nitrogen) Bases

• DNA has four different bases
• Cytosine C
• Thymine T
• Adenine A
• Guanine G

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• 2 categories of Nitrogenous Bases
• Purines double ring bases, A and G
• Pyrimidines single ring bases, T and C

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? Complementary Bases

• Nitrogenous bases on the 2 strands of DNA pair up
  with one another
• Cytosine pairs with Guanine with 3 Hydrogen Bonds
• Adenine pairs with Thymine with 2 Hydrogen Bonds

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? DNA Model