Morgan and Sturtevant: Chromosome Linkage Map based on recombination frequencies The farther apart genes are on a chromosome, the more likely to be separated during crossing over Recombina*on+frequencies+9%+9.5%+17%+b" cn"vg"Chromosome+Linked'genes'exhibit'less'than'50%'recombina7on'frequency.'Unlinked'genes'(i.e.,'far'apart'on'same,'or'on'different'chromosomes)'show'recombina7on'frequency'of'50%'The Molecular Basis of Inheritance • Chapter 16, pp. 305-317 • Experiments that demonstrated that DNA is the genetic material: Griffith’s transforming principle in Streptococcus bacteria Avery’s experiments Hershey and Chase experiments (in class) -DNA structure and ReplicationAlfred+Hershey+and+Martha+Chase,+1953+Fred+Griffith,+discovered+the+“transforming+principle”+Oswald+Avery+(in+the+picture),+Colin+MacLeod+and+Maclyn+McCarty+proved+that+Griffith’s+“transforming+principle”+was+DNA+The Search for the Genetic Material: Evidence that viral DNA can program cells T2 bacteriophage infecting an E. coli cell Bacteriophages"are"viruses"that"infect"bacterial"cells"Figure'16.3'Phage'head'Tail'Tail'fiber'DNA'Bacterial'cell'100+nm+Radioac*vity+(phage+protein)+in+liquid+Phage+Bacterial+cell+DNA+Centrifuge+Pellet+(bacterial+cells+and+contents)+Radioac7vity'(phage'DNA)'in'pellet'of'bacteria'Alfred Hershey and Martha Chase (1952) Showed that DNA is the genetic material of the phage, T2. Figure'16.4'Radioac7veRlabeled'protein'Radioac7veRlabeled'DNA'1+2+Ques7on'1'Human+DNA+has+30.9%+of+Adenine+nucleo*des.+Therefore,+the+%+of+guanines+in+the+human+DNA+is+:++A)+30.9%++B)+19.1%++C)+38.2%++D)+69.1%+Chargaff’s rules, 1950 In DNA from any cell and organism: 1. Number of purines equals the number of pyrimidines 2. The amount of guanine is equal to cytosine and the amount of adenine is equal to thymine Erwin+Chargaff+Ques7on'1'Human+DNA+has+30.9%+of+Adenine+nucleo*des.+Therefore,+the+%+of+guanines+in+the+human+DNA+is+:++A)+30.9%++B)+19.1%++C)+38.2%++D)+69.1%+Discovery of the DNA Structure: Watson, Crick & Franklin, 1953 (Nobel Prize, 1962) James+Watson+and+Francis+Crick,+figured+out+the+exact+structure+of+DNA+Rosalind+Franklin,+first+to+obtain+highaquality+DNA+crystals+and+their+Xaray+images.These+images+were+instrumental+for+Watson+and+Crick’s+discovery+of+the+DNA+structure.+Clicker question +DNA+double+helix+resembles+a+twisted+ladder++The+rungs+(steps)+of+ladder+(DNA)+are+the+_____.++A)+deoxyribose+sugars++B)+phosphate+groups++C)+hydrogenabonded+nitrogenous+bases++D)+sugaraphosphate+backbones++Figure'16.7a,'c'C+T+A+A+T+C+G+G+C+A+C+G+A+T+A+T+A+ T+T+A+C+T+A+0.34+nm+3.4+nm+(a)'Key'features'of'DNA'structure'G+1+nm+G+(c)'SpaceRfilling'model+T+ - two antiparallel sugar-phosphate backbones and - interior nitrogenous bases paired in specific combinations, adenine with thymine, and cytosine with guanine The Double HelixO+–O+O+OH+O+–O+O+O+H2C+O+–O+O+O+H2C+O+–O+O+O+OH+O+O+O+T+A+C+G+C+A+T+O+O+O+CH2+O+O–+O+O+CH2+CH2+CH2+5ʹ′+end+Hydrogen+bond+3ʹ′+end+3ʹ′+end+G+P+P+P+P+O+OH+O–+O+O+O+P+P+O–+O+O+O+P+O–+O+O+O+P+(b)'Par7al'chemical'structure'H2C+5ʹ′+end+Figure'16.7b+O+DNA'consists'of'two'an7Rparallel'polynucleo7de'chains'N+H+O+CH3+N+N+O+N+N+N+N+ H+Sugar+Sugar+Adenine'(A)'Thymine'(T)'N+N+N+N+Sugar+O+H+N+H+N+H+N+O+H+H+N+Sugar+Guanine'(G)'Cytosine'(C)'Figure'16.8'H+Base Pairs Watson and Crick reasoned specificity of pairing was dictated by ability of bases to form different number of H bonds adenine+and+thymine+form+two+bonds+cytosine+and+guanine+form+three+bonds+• In+DNA+replica*on,+the+strands+separate+– Enzymes+use+each+strand+as+a+template+to+assemble+the+new+strands+DNA replication depends on specific base pairing Parental'molecule'of'DNA'Both'parental'strands'se rve'as'templates'Two'iden7cal'daughter'molecules'of'DNA'Nucleo7des'A'A'DNA Polymerase is an enzyme that synthesizes a new DNA strand Figure'16.14'New'strand' Template'strand'5’+end+3’+end+Sugar+A'T'Base+C'G'G'C'A'C'OH+P+P+5’+end+3’+end+5’+end+ 5’+end+A'T'C'G'G'C'A'C'T'3’+end+Pyrophosphate+2++P+OH+Phosphate+Nucleoside+triphosphate+DNA+Polymerase+DNA Replication Fork: Animation http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html# After watching this animation, you should be able to explain the functions of the following enzymes and proteins: 1. Helicase 2. Primase 3. DNA Polymerase III 4. DNA Polymerase I 5.