chapter 4 - 9/5/2007 Chapter 4 "Modifications of Mendelian...

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9/5/2007 1 Chapter 4 “Modifications of Mendelian Ratios” Function and symbols of an alleles Incomplete dominance Codominance Multiple alleles Lethal alleles Combinations of two gene pairs and gene interaction Complementation Genes on the X-chromosome Sex limited and sex influenced inheritance Phenotype not related to genotype Extranuclear and Maternal Inheritance Specific phenotypes are often controlled by one or more gene pairs whose alleles exhibit modes of expression other than dominance and reccessive . In all such cases, however, the Mendelian principles of segregation and independent assortment are operative during the distribution of the alleles into gametes. Gene (allele) Action Quote of the Chapter The next major explosion is going to be when genetics and computers come together. I'm talking about an organic computer - about biological substances that can function like a semiconductor. Alvin Toffler author and futurist (“Future Shock”, 1970)
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9/5/2007 2 Biological Computers 1999: A computer made of neurons from leeches created. Bill Ditto, Georgia Institute of Technology Google biological computers 1997:DNA computing, Martyn Amos, PhD Thesis, University of Warwick, UK Types of Alleles 1. Wild- type” alleles -Allele most common in wild populations -Standards against which all mutations are compared 2. Mutant Alleles -modified alleles that have an altered gene product (protein) Symbols for Alleles Mendel’s notation: YY = Yellow seed coat color yy = green seed coat color Morgan’s notation (Drosophila): e + /e + = gray homozygote (wild type phenotype) e + /e = gray heterozygote (wild type phenotype) e/e = ebony homozygote (mutant phenotype)
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9/5/2007 3 Symbols for Alleles When the mutant is dominant to the wild type. Wr + /Wr + = normal wing (wild type phenotype) Wr + /Wr = wrinkled wing (mutant phenotype) Wr/Wr = wrinkled wing (mutant phenotype) Non Mendelian Gene Action 1. Incomplete (Partial) Dominance Heterozygote intermediate to the homozygotes 2. Codominance Expression of both alleles 3. Multiple Alleles More than one allele at a locus 4. Lethal Alleles Alleles that cause death 1. Incomplete or Partial Dominance
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9/5/2007 4 Note: Allele symbols do not denote dominance or recessive gene action!! 2. Codominance Expression of both alleles simultaneously Example: Blood Groups in Human For a glycoprotein on the surface of red blood cells Genotype Phenotype LM LM M LM LN MN LN LN N 3. Multiple Alleles: Blood Antigen in Humans Genotype Antigen Phenotype I A I A A A I A I
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This note was uploaded on 02/20/2008 for the course SORC 330 taught by Professor Brick during the Spring '08 term at Colorado State.

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chapter 4 - 9/5/2007 Chapter 4 "Modifications of Mendelian...

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