chapter 14 weinstein

chapter 14 weinstein - 1822-1884 Gregor MendelGregor Mendel...

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Unformatted text preview: 1822-1884 Gregor MendelGregor Mendel, an Austrian scientist wholived and conducted much of his mostimportant research in a Czechoslovakianmonastery, established the basis ofmodern genetic science. Heexperimented on pea plants in an effortto understand how a parent passedphysical traits to its offspring.After studying the data from theseexperiments, Mendel concluded thatphysical traits are passed to offspringthrough genetic factors called alleles.Each parent had not one but two allelesfor each trait. Four alleles (two from eachparent) interact to produce the finalphysical characteristics of an offspring.Blendingversus particulatemodels of heredityA genetic cross• Mendel was an experimentalistwith a fresh approach• Chose peas for hisexperiments, good choice:– self fertilizing but could be crossfertilized– 7 simple traits that bred true• Followed multiple generations• Quantitative approach14.2Mendel tracked heritablecharacters for three generations• P- parental• F1- first filialgeneration• F2- second filialgeneration• X= genetic cross wasperformed• Note the 3:1 ratio inthe the F214.3705224Alleles, different versions of a gene• There is a gene thatencodes a protein thatmakes flowers purple(P)• Another version of thegene fails to make thepurple color and theflowers are white (p)• P and p are differentalleles of the samegene14.4PpMendel’s law of segregation14.5Genetic terms• Dominant: P is dominant because in the hybrid F1 (Pp) all theplants are purple• Recessive: p is recessive for the same reason• Homozygous: individuals with two identical alleles- true breeding(PP and pp)• Heterozygous: individuals with two different alleles- will notbreed true (Pp)• Genotype: genetic make up of an individual• Phenotype: appearance of an individualIndividuals with the same phenotypecan have different genotypes• Pp and PP are bothpurple they have thesame phenotype• But they have adifferent genetic makeup: Pp is aheterozygote and PP isa homozygote• Genotype ratio isdifferent than thephenotype ratio14.6A test cross-how todetermine thegenotype of anindividual14.7Mendel’s law of independent assortment•Dihybrid cross•Two traits yellow/green(Y/y) and round/wrinkled(R/r)•F1 self-pollinated•Punnett square to set outgametes•Expected proportion ofphenotypes if the allelesassort independently...
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chapter 14 weinstein - 1822-1884 Gregor MendelGregor Mendel...

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