BIO Ch 24 - BIO 105 24.1 DNA structure and replication...

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BIO 105 24.1 DNA structure and replication Hershey and Chase experiments Determined that DNA is the genetic material Experiment 1 Viruses with DNA labeled with 32P were incubated with E.coli Mixed in a blender to remove virus particles attached to cells Centrifuged so bacteria formed a pellet Results- viral DNA was inside the bacteria Experiment 2 Viral proteins in capsids were labeled with 35S and viruses were incubated with E.coli Mixed in blender and centrifuged Results- labeled proteins were washed off with the capsids and were not inside the bacteria Discovering that DNA is the genetic material Structure of DNA Determined by Watson and Crick Double helix Composed of monomers called nucleotides Each nucleotide has 3 parts Phosphoric acid (phosphate) deoxyribose sugar Nitrogen base- 4 possible » Adenine and guanine- purine bases- double ring structure » Cytosine and thymine- pyrimidine bases-single ring structure DNA structure- ladder analogy DNA molecule consists of 2 chains of nucleotides Arranged in a “ladder” configuration Alternating phosphate and sugar groups form sides of ladder Rungs are composed of paired nitrogen bases Complementary base pairing-purine with pyrimidine » Adenine pairs with thymine » Guanine pairs with cytosine The “ladder” then coils to form a helix Overview of DNA structure Fig. 24.2 Replication of DNA Occurs during S phase of the cell cycle Each daughter DNA molecule consists of one new chain of nucleotides and one from the parent DNA molecule The 2 daughter DNA molecules will be identical to the parent molecule Before replication begins, the 2 strands of the parent molecule are hydrogen-bonded together
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This note was uploaded on 03/30/2008 for the course BIO 105 taught by Professor Mickle during the Spring '07 term at N.C. State.

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BIO Ch 24 - BIO 105 24.1 DNA structure and replication...

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