Lecture02

Lecture02 - BIS101/Engebrecht Lecture02 Announcements All...

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BIS101/Engebrecht Lecture02 4/1/10 Announcements: All lectures are podcasted, you can find the podcasts on SmartSite. No discussion sections this week. There were some problems with the online quiz - I believe these are now fixed (this is as of noon on Thursday – please re-download the pdf, there have been changes). I still highly recommend that you do the quiz from the pdf file before going online to input your answers. Remember that the actual order of the answers may be different on-line so don’t just copy the letter answer you have on the pdf into the quiz. The quizzes are due April 9 th . I viewed Tuesdays lecture as an overview – there will be no specific questions from the lecture on the midterm. We discussed Mendel and the importance of his findings to the field of genetics: Mendel 1822-1884; published his study in 1865. At this time there was no understanding of DNA as the hereditary molecule. “Blending” was the favored hypothesis of the time. Mendel used the garden pea, Pisum sativum , as his model organism. The advantages were, it is inexpensive, is easy to obtain and maintain, does not require a lot of space, and has a relatively short generation time (could do several crosses in a season), and produces lots of offspring. In addition, peas can self-fertilize or be cross-fertilize. Mendel set up controlled crosses to determine the laws of heredity. He showed a defined and reproducible ratio of phenotypic classes in the F2 of a monohybrid cross. His success was due to his choice of model organism and the large number of progeny he was able to look at. He looked at seven discontinuous traits that he followed through his crosses. He spent two years selfing plants with the same characteristics to generate true breeding lines. True breeding means that an organism with a particular, inheritable phenotype produce only offspring with that (same) phenotype . I drew on the board the monohybrid cross using round vs. wrinkled seed shape. P RR x rr F1 All round; Rr (therefore round is dominant and wrinkled is recessive) F2 (generated by selfing the F1) 3 round to 1 wrinkled. You can also describe the outcome of the crosses using a punnett square.
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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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Lecture02 - BIS101/Engebrecht Lecture02 Announcements All...

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