Lecture11S10 - BIS101/Engebrecht 4/23/2010 Lecture11...

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1 BIS101/Engebrecht 4/23/2010 Lecture11 Announcements: The mean for Midterm I was 65; grades are posted on SmartSite. Today is National DNA Day. The second third of the course will concentrate on the central dogma and how genetics has been instrumental in elucidating the basic principles, primarily using E. coli as a paradigm. DNA structure The central dogma in biology is, DNA RNA protein. We will now discuss the properties of DNA that allow it to faithful replicate itself and store genetic information. I reminded you that this is not a straight linear pathway. For instance, we saw that RNA can make DNA, an important mode of replication of retroviruses like HIV. The proof that DNA was the hereditary material came from a few key experiments performed in the 1920s, 40s and 50s (prior to the elucidation of the DNA structure). These experiments combined genetic and biochemical approaches to definitely show that DNA was indeed the blueprint of life. I posted a handout ( Handout11 ) that emphasizes the key points in these experiments and I also refer you to your book. One aspect that was difficult for people to understand was how such a simple molecule could provide all of the information necessary to make a complicated multicellular organism. The elucidation of the DNA structure provided the answer to this question. We discussed what DNA as the hereditary material must fulfill: 1) it must have informational content 2) the information must be stable, 3) but have the ability to change 4) it must be able to faithfully reproduce itself Prior to Watson and Crick’s model of DNA, scientist knew the chemical building blocks of the DNA molecule. They knew that DNA was made up of four nucleotides. Nucleotides are comprised of a phosphate group, a deoxyribose sugar and 1 of 4 bases (adenine, cytosine, guanine and thymine). Thus, the adenine nucleotide is formally written as deoxyadenosine 5’ monophosphate. In contrast, a nucleoside is the base and sugar and would be deoxyadenosine. Another important piece of the puzzle came from the work of Chargaff.
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This note was uploaded on 07/02/2010 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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Lecture11S10 - BIS101/Engebrecht 4/23/2010 Lecture11...

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