section7_ak - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Recitation Section 7 Answer Key February 28-March 1, 2005 Molecular Biology—DNA as Genetic Material and DNA Replication A. DNA as Genetic Material Before people used words such as “genetic material,” the concept behind this term was well established. In fact, an entire industry based in large part on this concept played an enormous role in the development of our civilization. 1. What is this industry? How was the concept of “genetic material” central, if not articulated, part of this industry? Agricultural breeding programs have been in existence for millennia and have allowed our civilization to expand as people’s capacity to produce enough food to feed the expanding population also grew. At the heart of these programs is the understanding that all living things possess heritable traits that are passed down from generation to generation. Breeding programs rely on controlled crosses and artificial selection to isolate and propagate species with particular desirable heritable traits. After the work of Mendel was re-discovered, trying to understand what that “genetic material” was became a key part of scientific endeavor. While scientists did not discover what that substance was for some time, they fairly quickly formulated the three requirements that genetic material must satisfy. 2. What are those requirements? Why do they make sense? Genetic material must Encode genetic information Pass that information on to offspring (replicate) Change that information (mutate) Observations of heritable traits indicate that genetic information must be recorded somehow and also must be passed on to offspring. In addition, change over time indicates that there must also be a mechanism that allows the information to be changed. 3. Given what you now know about DNA structure, how does DNA satisfy these requirements? Information is encoded in the sequence of DNA bases. Because DNA is complementary and paired, one strand of DNA gives rise to two identical strands in DNA replication. That allows for production of two cells carrying identical copies of genetic material. If, as a result of environmental factors, or as a result of normal processes during
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This note was uploaded on 05/02/2009 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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section7_ak - MIT Department of Biology 7.014 Introductory...

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