DNA Replicat

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DNA Replication
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What does DNA stand for?

• D deoxyribo N nucleic A acid
• Put it all together and it spells-
• deoxyribonucleicacid

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What is DNA Replication?

• Process by which-
• a cell makes a copy of the DNA in its nucleus.

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When does DNA Replication occur? Before
Mitosis begins- Interphase

Cell Division Stage1- Interphase
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• Why is DNA Replication an important cell process?
• Ensures that each daughter cell will have all of
  the genetic information it needs to carry out its
  activities.

Forming daughter cell
DNA (genetic information)
Forming daughter cell
DNA (genetic information)
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History of DNAs Discovery

• 1950s scientists showed DNA carries all
  cells instructions.
• Learned DNA passed from parent cell to its
  daughter cells.
• 1953 James Watson and Francis Crick discovered
  structure of DNA.
• - Revealed important information about how
  DNA copies (replicates) itself.

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Appearance of DNA

• Looks like spiral staircase or twisted ladder
• Often called double helix
• helix-
• shape that twists like threads of a screw

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Structure of DNA
Phosphate

• Sides (DNA Ladder)
• Alternating molecules of
• Deoxyribose sugar
• Phosphate
• Rungs (DNA Ladder)
• Made up of pairs of nitrogen bases
• adenine
• thymine
• cytosine
• guanine

Deoxyribose sugar
Nitrogen base
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Ladder Rungs

• Letters A, T, G, C
• Used to represent the four bases that make up
  ladders rungs
• Nitrogen bases on one side of ladder match up
  in specific way with bases on the other side.
• Adenine always pairs with Thymine (A-T)
• Guanine always pairs with Cytosine (G-C)

Nitrogen Base
Nitrogen base
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• Pairing pattern of the nitrogen bases
• key to understanding how DNA replication occurs.

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Replication Process

• Step 1
• Two sides of the DNA molecule unwind and separate
  between paired nitrogen bases on each rung.
• Like a zipper unzipping

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Replication Process

• Step 2
• Nucleotides floating in nucleus pair up with
  bases on each half of the DNA molecule.
• A always pairs with T
• G always pairs with C

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Replication Process

• Step 3
• Once new bases are attached, two new DNA
  molecules formed.
• Order of bases in each new DNA molecule exactly
  matches the order in the original molecule.

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• http//www.cfkeep.org/uploads/dna_replication.mov

http//video.search.yahoo.com/search/video?pdnas
tructureeiUTF-8frsbc-webxwrt
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(No Transcript)
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Applying What You Have Learned

• Lab
• Marshmallow DNA Replication
• Write down a code of 5 base pairs
• Ex A-T, T-A, G-C, G-C, T-A
• Using colored marshmallow make your base pairs
  and place them in the order of your code
• Green Adenine Yellow Thymine
• Pink Guanine White Cytosine
• Use a broken demonstrated shown
• Make sides of ladder, as demonstrated
• Deoxyribose
• Phosphate

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• Base-Pairing Mini-Lab
• Materials
• Small Marshmallows of 4 different colors
• Large White marshmallows
• Small White marshmallows
• Toothpicks
• Directions
• Use your knowledge of how the base pairs of DNA
  bond to create an accurate model of a DNA code
  that is handed to you at the start of the lab
• Use the colored marshmallows to represent the
  different base pairs, the large white
  marshmallows to represent the sugar, and the
  small white marshmallows for the phosphate
  groups. Keep in mind that purines bases are
  larger than pyrimidine bases!
• Record your random 7-digit code here
  ___________________________________
• Use the space below to create a key that will
  identify the parts of the model, and their
  corresponding parts in DNA
• Follow-up Questions
• 1. What is the sugar that makes up DNA?
• 2. How does the number of adenines compare to
  the number of thymines? How about cytosines to
  guanines? Provide sample numbers.
• 3. How do the number of purines compare to the
  number of pyrimidines? Provide sample numbers.

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• DNA Extraction Lab