Using genes:

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Using genes DNA and Transcription
Ch. 12, pages 206 - 214
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Molecular Biology in the 1940s
Proteins?
or
Nucleic Acids?
3
Plant Biology at Cambridge
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Structure Code
We found the secret of life!
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DNA Codes for Proteins

• Proteins
• Structural
• Storage
• Enzymatic
• Control the chemistry of the cell.

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Chromosome Organization
In nucleus
Chromatin - DNA histones
histones
Fig. 12-1Pg. 208
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Deoxyribonucleic AcidDNA
DEOXYRIBO NUCLEIC ACID
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Components of DNA

• Deoxyribose 5-carbon sugar lacking oxygen
  (-OH)
• Phosphate group
• Nitrogen bases

Adenine
Thymine
Cytosine
Guanine
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Nucleotide Structure
base
deoxy
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Simple Organization of DNA
Phosphate
T
Deoxyribose
Nitrogen base
Sugar
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DNA
12
DNAReplication
A replicationfork -- aidedby DNA polymerase
Fig. 12-3 pg. 210
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Semi-conservative Replicationof DNA
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How do genes represented by the code of DNA
stored in the nucleus become expressed in the
cell?
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RNARibo Nucleic Acid

• Ribose sugar in place of deoxyribose
• Uracil in place of thymine
• Usually single stranded
• Shorter than DNA molecules
• Shorter-lived than DNA molecules

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3 Kinds of RNA

• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)

• Messenger RNA (mRNA)

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Transcription
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Transcription
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Transcription
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Lecture Activity
Given the following template strand base sequence
on the DNAA G T T A C G T A C C G
1. What would be the complementarygene strand
base sequence of DNA?2. What would be the
transcribed base sequence of mRNA? Use Block
Letters.
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Transcription
DNA mRNA
Translation
mRNA Protein
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(No Transcript)
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(No Transcript)
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mRNA Produced Off of DNA

• Adenine paired from DNA thymine
• Cytosine paired from DNA guanine
• Guanine paired from DNA cytosine
• Uracil paired from DNA adenine

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A Wry Statement in Nature(Watson Crick)
"It has not escaped our notice that the specific
pairing we have postulated immediately suggests
a possible copying mechanism for the genetic
material."