Lecture 11 SLIDES

Plant seeds from pod from pod 5 examined first

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Unformatted text preview: urple or white flowers matured into pod 4 Planted seeds 2. Plant seeds from pod from pod 5 Examined First generation offspring (F1) offspring: all purple flowers 3. Examine and quantitate offspring flower color…. Figure 14.2 Mendel’s breeding experiments: two-generational crosses Experimental Design: “P generation” (the first cross) Hybridization of 2 true-breeding varieties The Experimental Basis for Mendel’s Law of Segregation Results: ! P Purple flowers White flowers P ! Purple flowers White flowers P white x purple F1 F1 “F1 generation” (used for the second cross) The hybrid offspring of P generation All plants had purple flowers F1 All offspring were purple All plants had purple flowers “F2 generation” (the results!) The offspring of self-pollinated F1 individuals F2 F2 many purple (n=705), some white (n=224) F2 Ratio of 3:1 of purple:white Figure 14.3 Figure 14.3 The Experimental Basis for Mendel’s Law of Segregation Mendel Concluded: 1.  purple flower color is dominant, and white flower color recessive white flower color was not lost, but retained over to next generation P ! Purple flowers White flowers Conclusion 1: Dominant vs. Recessive Traits Mendel observed only purple flower “factor” affected F1 hybrid flower. F1 Mendel reasoned that: All plants had purple flowers 2.  –  Purple flower color factor was dominant in F1 –  White flower color factor was recessive in F1 (traits were NOT blended from generation to generation) F2 Figure 14.3 Conclusion 2: Recessive Traits Skipped Generations Mendel observed white flower factor reappeared in F2 in 3:1 ratio. Mendel observed the same 3:1 inheritance among F2 offspring for many other characters. Mendel reasoned that: –  The 3:1 ratio revealed flower color factor was inherited as a discrete “particulate” trait (traits were NOT blended from generation to generation) Table 14.1 Mendel’s Model for The Law of Segregation Mendel developed a hypothesis based on four related concepts: 1 1. Alternative versions of genes account for variations in inherited characters Alleles is the term for alternative version of genes Allele for purple flowers 1 1 . Alternative versions of genes account for variations in inherited characters. 2. 2 For each character, an organism inherits two alleles, one from each parent. 3. 3 If two alleles differ, the dominant allele determines character appearance. Locus for flower-color gene 4. 4 Two alleles for a heritable...
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This note was uploaded on 04/03/2010 for the course BIOLOGY BILD 1 taught by Professor Traver during the Winter '10 term at UCSD.

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