BBAabbaGametesBParentalaRecombinantB5-16
5-16 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display A A a a B B b b Gametes a B A B A b a b x Parental Recombinant
Experimental evidence ofreciprocal chromosomalexchangeingeneticrecombinationReported in1931-Genetic recombination depends onthereciprocal exchangeof parts betweenmaternal andpaternalchromosomes.Harriet Creighton and Barbara McClintock's work on corn.CurtStern'sworkonfruitflies.5-17
5-17 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Experimental evidence of reciprocal chromosomal Experimental evidence of reciprocal chromosomal exchange in genetic recombination exchange in genetic recombination Reported in 1931 Reported in 1931 – Genetic recombination depends on Genetic recombination depends on the reciprocal exchange of parts between maternal and the reciprocal exchange of parts between maternal and paternal chromosomes. paternal chromosomes. Harriet Creighton Harriet Creighton and Barbara McClintock Barbara McClintock ’s work on corn. s work on corn. Curt Stern Curt Stern ’s work on fruit flies. s work on fruit flies
CurtStern(1902-1981),UCBerkeleyXYAXXY2Identification of physicalmarkerstokeeptrack ofAod 4 Hhitaspecific chromosomepartsloenabled researchers to testtheidea.Geneticmarkerswerepoints of reference todetermine if particularprogeny were result ofrecombination5-18
5-18 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Curt Stern Curt Stern (1902 -1981), UC 1981), UC Berkeley Berkeley Identification of Identification of physical physical markers markers to keep track of to keep track of specific chromosome parts specific chromosome parts enabled researchers to test enabled researchers to test the idea. the idea. Genetic markers Genetic markers were points of reference to points of reference to determine if particular determine if particular progeny were result of progeny were result of recombination. recombination
Genetic recombination between car and Bar genes ontheDrosophilaXchromosomeAdditionalmaterialfromDiscontinuitypartoftheYchromosomeBarcarParental(Q)chromosomescartBar+MeiosisNocrossing-overCrossing-overBarBarcarcarcartBartBartcartBarBartcarcarParentalRecombinantChromosomestransmittedtocartBartprogeny（）cartBarParentalRecombinant5-19Fig.5.6
5-19 Fig. 5.6 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Genetic recombination between Genetic recombination between car and Bar genes on genes on the Drosophila Drosophila X chromosome X chromosome
Chiasmata mark the sites of recombination(a)Duplicatedchromosomehomologs234Synapsis(b)Chiasmatabecomevisible(sitesofcrossing-over)(c)Fig.5.7a-c5-20
5-20 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Chiasmata Chiasmata mark the sites of recombination mark the sites of recombination Fig. 5.7 a-c