For "JOYMERCY" Only!!! Assign #4
AlphaMann
dna-replication_bio-studyguide1.pdf
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DNA replication
What is DNA?
• It is your genetic material or “program.”
• Passed from cell to cell.
• DNA can give clues to mysteries!
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How do we know DNA controls the cell and its activities?
Major experimental achievements:
• Frederick Griffith (1928)
• Alfred Hershey and Martha Chase (1950)
• Erwin Chargaff (1947)
• Maurice Wilkins and Rosalind Franklin (1950)
• James Watson and Francis Crick (1953)
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Frederick Griffith
Hershey and Chase
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Viruses are unique organisms…
Erwin Chargaff
• Chargaff worked with nucleotides. – Adenine, guanine, cytosine, thymine.
• He discovered that DNA is species specific.
• Chargaff’s Laws – Adenine = Thymine
– Guanine = Cytosine
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DNA and RNA are the polymers of nucleotides.
• Nucleotides are “monomers.”
• DNA and RNA are “polymers.”
• These large DNA and RNA molecules direct cellular activities.
DNA base pairs:
Notice how they bond together.
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Rosalind Franklin
• First scientist to determine the P-S outer structure of DNA, but using x- ray crystallography. – Her evidence gave clues to the
“twisted ladder” structure of DNA. – Without this data, its structure could
not have been discovered.
• She died prior to receiving the credit
she deserved. – She did not receive a Nobel Prize.
Watson and Crick
• Published the final version of what the DNA molecule looked like.
– April 1953 “Nature”
• They received the Nobel Prize.
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There is a lot of information coming at you!
• These slides should help you understand the material.
• You need to attend lecture, in order to really get this material.
• Don’t get scared – this isn’t that bad!
Where do you find DNA?
It all starts in the nucleus.
The chromosome has DNA twisted within it.
The DNA’s nucleotides.
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Purines vs. Pyrimidines
• Pyrimidines have one ring.
• Purines have two rings.
• One pyrimidine always pairs with a purine.
What is the structure of DNA?
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DNA only grows in the 5’ → 3’ direction?
The structure of this sugar explains why I lectured on the 5’ to 3’ direction of DNA replication.
The DNA ladder is “antiparallel.”
Notice that each side of the DNA strand grows in
opposite directions.
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These mirror images help DNA to make a copy of itself.
DNA replication is “semi-conservative.”
This means that in each daughter cell, an original strand of DNA is present.
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An overview of DNA replication.
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Leading Strand vs. Lagging Strand
DNA Quiz Don’t turn this in – this is for you!
• Where do you find DNA in prokaryotic cells? Eukaryotes?
• What four nucleotides make up DNA?
• Which nucleotides pair up to one another?
• Which nucleotides are pyrimidines?
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DNA Quiz Don’t turn in!
• Why does DNA grow in the 5’ → 3’?
• What makes the “rungs” of the ladder?
• What makes the “sides” of the ladder?
• Why is replication “semiconservative”?
• What are “leading strands”?
• What are “lagging strands”?
Now what?
• Draw the steps of DNA replication. – Try to relate this to your cells.
• When does this happen and why? – How does tie into mitosis or meiosis?
– When would your body need to make DNA?
