Chapter 14 Learning Objectives

Chapter 14 Learning - Chapter 14 Learning Objectives-Understand that generation of phenotype may require the multiple interactions of molecular

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Chapter 14 Learning Objectives -Understand that generation of phenotype may require the multiple interactions of molecular, biochemical and/or developmental processes and how this impacts data generated by genetic experimentation. Different alleles of a gene may cause phenotypic differences, but an allele cannot determine a phenotype by itself : many other genetic and environmental contributions are needed to produce a phenotype. Determination of many diseases involves a complex series of steps each of which is a possible site for genetic or environmental variation to act. (Ex. PKU causes mental retardation) is considered a simple autosomal recessive disease caused by defective allele of the gene coding for the liver enzyme PAH. There are exceptions to this simple model such as mutations in genes other than the gene for PAH such as the gene for tetrahydrobiopterin which can cause hyperthenylalaninemia. Gene Action- is a term that embraces the complete set of events that begins with the gene's DNA sequence and leads all the way to the observed phenotype. (These steps generally constitute a long and complex network involving interactions between genes and the environment.) -Explain the purpose of a complementation test, how you categorize results as complementation vs. no complementation, and what these different results indicate. Complementation- The production of a wild-type phenotype when two recessive mutant alleles are brought together in the same cell. A complementation test is used to determine if mutant alleles are alleles of one gene or of different genes. In a diploid organism, the complementation test is performed by intercrossing homozygous recessive mutants two at a time and observing whether or not the progeny have the wild-type phenotype. If recessive mutations represent alleles of the same gene, the obviously they will not complement each other, because they both represent loss of the same gene function. Recessive Mutant X Recessive Mutant = Recessive Mutant DO NO COMPLEMENT > alleles of same gene Two recessive mutations in different genes would have a wild-type function, provided by the respective wild-type alleles. Recessive Mutant X Recessive Mutant = Wild Type phenotype COMPLEMENT > mutation in different genes *Important* it is easy to think that mutants complement each other but its important to remember the active agents in complementation are the proteins produced by the wild-type alleles.
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In a haploid organism, the complementation test cannot be performed by intercrossing. Alternative make heterokaryon = when the nuclei from two different fungal cells come to occupy one cell. This occurs since fungal cells readily fuse together. Then use same logic as complementation test to see if wild type emerges. -Analyze a complementation table to determine the number of genes affecting a single
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This note was uploaded on 04/24/2008 for the course BIO 224 taught by Professor Halsell during the Spring '08 term at James Madison University.

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Chapter 14 Learning - Chapter 14 Learning Objectives-Understand that generation of phenotype may require the multiple interactions of molecular

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