Lect10 - Lecture 10 What is a gene

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1 Lecture 10 What is a gene Each chromosome has one DNA molecule Each chromosome has many genes A gene produces a protein that give rise to a phenotype A gene has many forms- alleles Different alleles are caused by different mutations in the same gene Mutations in different genes can give you the same phenotype yellow blanco Shaven body Forked bristle white w1 w2 w3 chromosome Many genes Genes on DNA Mutations in a gene
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2 Complementation The complementation test is a rapid method of determining whether two independently isolated mutants with the same phenotype are in the same or different genes. Ornithine Citruline Arginine Enzyme1 Enzyme2 Both mutant1 and mutant2 cannot make arginine. Are these two different mutations in the same gene or Mutations in two different genes If you are working with Neurospora, you can feed the intermediate (Citruline) to the mutants and see if they can now make arginine. Mutant1+ citruline=arginine Mutant2+citruline=mutant It is not often this easy. The wildtype eye color in flies is red Say two different laboratories isolated mutants in that had white eyes. You cant feed flies eye color precursor to figure things out!
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3 Naming mutants It is not often this easy. The wildtype eye color in flies is red Two mutants are ISOLATED BY TWO DIFFERENT LABS Mutant flies have white eyes. The researcher who identified the first white eyed mutant lived in the US and named it white. Small case w designates the recessive mutant allele Upper case W designates normal (dominant) wildtype The researcher who identified the second mutant lived in Spain and named it blanco. Small case b designates recessive mutant allele Upper case B designates normal (dominant) wildtype allele The researcher who isolates the mutant names it!!!!! Cheapdate Cockeye king tubby Sevenless Bride of sevenless Daughter of sevenless
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4 White and Blanco Precursor (white) Intermediate (white) Product (red pigment) Enzyme1 Enzyme2 Gene1 White Gene2 Blanco Precursor (white) Product (red pigment) Enzyme1 Gene1 Blanco=White???? OR QUESTION Are the two independently isolated mutations disrupting the same or different genes.
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5 White gene Mapping genes takes lots of crosses and is time consuming There is an easier way! If the two mutations map to different regions of the X- chromosome then that would indicate that they are two different genes. You could map each mutation. If the two mutations map to The same regions of the X-chromosome then that would indicate that they are the SAME GENE
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6 Easy way!!!
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