A1258150112rDWJm

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Chapter 2
The Molecular Nature of Genes
Page 18-27
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DNA
1869, Friedrich Miescher discovered in the cell
nucleus a mixture of compounds --
nuclein. Nuclein contains deoxyribonucleic acid
(DNA).
At the end of 19th century, chemists learned the
structure of DNA and a related compound,
ribonucleic acid (RNA)
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A nucleotide is composed of a sugar, a phosphate
group and a base
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A nucleotide is composed of a sugar, a phosphate
group and a base
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A nucleotide is composed of a sugar, a phosphate
group and a base
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A nucleotide is composed of a sugar, a phosphate
group and a base
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What is the carrier of genetic information?
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avirulent
virulent

avirulent
virulent
Frederick Griffith, 1928
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What is the chemical nature of the transforming
material

1. Resistant to organic solvent and proteases -- it
   is not a protein
2. Resistant to ribonuclease -- it is not an RNA
   molecule
3. Sensitive to deoxyribonuclease -- it is likely a
   DNA molecule

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Do Griffiths and Avery/McLeod/McCartys
experiments together convince you that DNA is the
carrier of genetic information

1. Absolutely yes
2. Absolutely No
3. Partially, but not definitive
4. Most likely not true, but it could be right
5. What if there is a fourth important molecule that
   we dont know

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T2 Bacteriophage
Bacteriophages are composed of only DNA and
proteins.
A bacteriophage infects and reproduces inside a
bacterial cell
A.D. Hershey and Martha Chase, 1952
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P
S
A.D. Hershey and Martha Chase, 1952
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The chemical nature of DNA and RNA
DNA
RNA
Adenine (A) Cytosine C Guanine (G) Thymine (T)
Adenine (A) Cytosine C Guanine (G) Uracil
(U)
Sugar deoxyribose
Sugar ribose
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nucleosides
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nucleotides
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Adenosine-5-monophosphate (AMP)
Adenosine-5-diphosphate (ADP)
Adenosine-5-triphosphate (ATP)
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3
5
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5 TCA 3
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You can distinguish DNA from RNA by the following
characteristics

1. The number of phosphate groups
2. One contains U and one does not
3. The number of purine bases
4. The sugar base (ribose vs. deoxyribose)
5. The length of the polymer