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DNA

DNA. __________ concluded that the genetic material injected into bacteria by bacteriophage was DNA. __________ was the first to conclude that bacteria could be transformed by a then unknown genetic factor. DNA is a polymer that is made of monomer units called _______________.

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DNA

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  1. DNA

  2. __________ concluded that the genetic material injected into bacteria by bacteriophage was DNA. • __________ was the first to conclude that bacteria could be transformed by a then unknown genetic factor. • DNA is a polymer that is made of monomer units called _______________. • The sugar in these monomer units is _____________.

  3. Deoxyribonucleic Acid • Defined: Molecule that stores genetic information • Nucleotides: Three repeating units of nucleic acids • 1) Sugar • 2) Phosphate Group • 3) Nitrogen Base • Millions of nucleotides per strand of DNA

  4. DNA is a 3- Dimensional Molecule. It is shaped like a twisted ladder. The sides are made of alternating sugar and phosphate groups. The ladder steps or rungs are made of the bases.

  5. Double Helix • James Watson and Francis Crick identified DNA’s structure in 1953 • Double Helix: spiral shape of DNA • The two nucleotide strands are connected by hydrogen bonds between the bases

  6. Nucleotides • Sugar (Deoxyribose) alternates with the phosphate group • 4 Different Bases: • Adenine (A) • Thymine (T) • Guanine (G) • Cytosine (C) • Rule: A always joins with T • Rule: C always joins with G • Chargaff wrote this rule • Human DNA: ~3 Billion base pairs C T A A T G T

  7. How many Nucleotides?

  8. Take out the nucleotides you cut out at home and turn them face down on your desk. Select 6 of them and line them up in a vertical column. Write down the LETTER of the nitrogen containing base (A, T, C, or G) where it says left side on your worksheet. Now, write the complementary base in a column where it says right side. Look at the sequence of the person sitting near you and write down that left and right sequence on your paper. Are the two left sequences the same?

  9. Now, select one 6-nucleotide sequence of your cut-out nucleotides and use the remaining nucleotides (yours and your partners) to make the complementary strand. Work together. Make sure that the bases pair up correctly. Answer questions #1-5 on your paper. If you finish early, think about how many words you can make from the letters s, t, a, and e. How many words could you make if you include nonsense words? How many words could you make if you could repeat letters (but still only use 4 letters in total at a time, such as: aatt, or saee)?

  10. How many DIFFERENT combinations of bases could you make if there are 4 different bases (A, T, G, C) and there are 6 spaces to put them in? DNA works as the genetic material because the bases of the nucleotides can be combined into so many different sequences that the DNA can carry a large amount of information.

  11. Simons Says: • Name the three parts of a DNA nucleotide. • Name the four nitrogen bases and how they pair with others. • Fill in the missing DNA nucleotides: A C ? T ? ? ? G C T ? ? A ? C ? T T ? ? C ? T A T ? ? ? C A ? G ? G ? ? • Can you find the wrong base pairing? T A G G C C T G T C G A A C A G T A T C C G G A C A A C T T G T C A

  12. When do cells need to replicate their DNA? DNA replicates before mitosis and before meiosis How can the DNA molecule make an exact copy of itself if it is made of 2 strands bonded together? YES! The strands need to break the hydrogen bonds and separate from each other in order to replicate!

  13. DNA Replication • Defined: Process of copying DNA • During interphase (S-stage) • Step 1: DNA Helicase “unzips” the two DNA strands (breaks the H bonds) • Step 2: Free floating nucleotides (A, T, C, G) match up • Step 3: DNA Polymerase reconnects the two strands

  14. DNA Polymerase Glues the DNA T A A T G C G C Two Identical Strands of DNA! A T C G T A A T G C G C C G T A C G A T DNA Helicase Splits the DNA

  15. List what takes place during the steps of DNA replication.

  16. Accuracy & Repair • Mutation: change in DNA sequence • Mutations can be corrected • Enzyme “proofreads” DNA and check/correct errors • Pre-repair: 1 in 10,000 nucleotides has an error • Post-repair: 1 in 1 billion nucleotides has an error

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