NOTES: 12.1 - DNA (History; Identifying the Substance of Genes)
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Transcript of NOTES: 12.1 - DNA (History; Identifying the Substance of Genes)
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NOTES: 12.1 - DNA(History; Identifying the
Substance of Genes)
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What we’ve learned so far…
● Cells make proteins
● Genetic information is passed
on through chromosomes
● Compacted DNA and proteins = chromosomes
● Genetic information is stored in the nucleus
● Genetic information is essential; each cell must receive all info. (ensured by MITOSIS)
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To truly understand genetics, biologists first had to discover the chemical nature of the gene.
How do genes control what you look like?
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Vocabulary:● Transformation
● Bacteriophage
Key Concepts:
● What did scientists discover about the relationship between genes and DNA?
● What is the role of DNA in heredity?
12-1 DNA
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DNA’s “Experiment” History
● For thousands of years, humans have noticed that parents pass on traits to their offspring…
● What is the process and/or molecule that makes this possible…??
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DNA’s “Experiment” History
• Frederick Griffith: How do certain types of bacteria cause pneumonia? – The experiment that tested this
question led to new knowledge.
– Genetic information could be transformed (passed) from one bacterium to another.
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Genetic Info. Transferred
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TRANSFORMATION● Heat killed pathogenic bacteria had passed their
disease-causing ability to the harmless strain
● Griffith called this TRANSFORMATION– One strain of bacteria (harmless) had changed
into the other (harmful, or disease-causing)
● Some factor was transferred from the heat killed cells to the live cells– This factor might contain a GENE with
information that could change harmless bacteria into disease causing ones!
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Avery & DNA● Oswald Avery’s group of scientists decided to
repeat Griffith’s experimentto determine which MOLECULE in the heat
killed bacteria was needed for transformation● Made an extract (juice) from heat killed bacteria
and added enzymes that destroy proteins, carbohydrates, & lipidsTransformation still occurred!
● Repeated the experiment but added enzymes that destroy DNA Transformation DID NOT occur!!
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Avery’s Conclusion
● Avery’s Conclusion: DNA is the substance that stores and transmits genetic info. from generation to generation
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Hershey-Chase Experiment
● They studied viruses; specifically bacteriophages– Bacterio = bacteria – Phage = eater
● Viruses are made up of: – DNA + protein coat
● Research Question: Which part of the virus enters the infected bacteria cell?
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● They grew viruses in the presence of radioactive markers 32P and 35S. – Sulfur is found in protein coat– Phosphorus is found in DNA
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Hershey-Chase Conclusion:
● after viruses had infected the bacteria, bacteria were collected & tested for radioactive 35S and 32P
● nearly all of the radioactivity in the bacteria was from phosphorus!
● Genetic information of the bacteriophage that was passed into the infected bacteria was DNA (NOT protein!)
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No Sulfur! Phosphoru
s!
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Hershey-Chase Conclusion:
● their experiment confirmed Avery’s results
● this convinced many scientists that DNA was the genetic material found in genes…not just in viruses and bacteria, but in all living cells
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What does DNA do?
● Storing information: the genes that make flowers purple must somehow carry that information; blood type, eye color; patterns of development
● Copying information: before a cell divides, it must make a complete copy of every one of its genes
● Transmitting information: genes are transmitted from one generation to the next
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HOW does DNA…
• Store information?
• Copy information?
• Transmit information?
-first, we must understand the STRUCTURE
of DNA!!...next time!