Mapping the Distance Between Genes. Linkage Map. Linkage Map. Alfred Sturtevant. Student of Morgan. Constructed a gene1c map

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Alfred Sturtevant Mapping the Distance Between Genes Student f Mrgan Cnstructed a gene1c map an rdered list f the gene6c lci alng a par6cular chrmsme Predicted that The farther apart tw genes are q

units Expressin f distances between genes ne map unit, r cen8mrgan, represents a 1% RESULTS recmbina6n frequency Chrmsme Map units indicate rela6ve distance and rder, nt precise lca6ns f genes

1 Alfred Sturtevant Mapping the Distance Between Genes Student f Mrgan Cnstructed a gene1c map an rdered list f the gene6c lci alng a par6cular chrmsme Predicted that The farther apart tw genes are q the higher the prbability that a crssver will ccur between them Ø and therefre the higher the recmbina8n frequency Linkage map Linkage Map gene6c map f a chrmsme based n recmbina6n frequencies Map units Expressin f distances between genes ne map unit, r cen8mrgan, represents a 1% RESULTS recmbina6n frequency Chrmsme Map units indicate rela6ve distance and rder, nt precise lca6ns f genes Recmbinatin frequencies 9% 9.5% 17% b cn vg Linkage Map Genes that are far apart n the same chrmsme Can have a recmbina6n frequency near 50% Such genes are physically linked, but gene6cally unlinked, And behave as if fund n different chrmsmes 1

Sturtevant Gene Mapping Used recmbina6n frequencies t make linkage maps f fruit fly genes Chrmsmal banding Staining methd t iden6fy regins f

Due t densely packaged gene- free regins f chrmsmes Fig. 15-12 Shrt aristae Mutant phentypes Black bdy Cinnabar Vestigial wings Brwn 0 48.5 57.

5 Lng aristae (appendages n head) Gray bdy Red Nrmal wings Wild-type phentypes Red Altera1ns f chrmsme number r structure Large- scale chrmsmal

2 Sturtevant Gene Mapping Used recmbina6n frequencies t make linkage maps f fruit fly genes Chrmsmal banding Staining methd t iden6fy regins f chrmsmes Gene6cists can develp cytgene6c maps f chrmsmes Cytgene1c maps Indicate the psi6ns f genes with respect t chrmsmal features Ie bands Due t densely packaged gene- free regins f chrmsmes Fig Shrt aristae Mutant phentypes Black bdy Cinnabar Vestigial wings Brwn Lng aristae (appendages n head) Gray bdy Red Nrmal wings Wild-type phentypes Red Altera1ns f chrmsme number r structure Large- scale chrmsmal altera6ns OPen lead t spntaneus abr6ns (miscarriages) Or cause a variety f develpmental disrders Nndisjunc1n Pairs f hmlgus chrmsmes r sister chrma6ds d nt separate nrmally during meisis As a result One gamete receives tw f the same type f chrmsme q And anther gamete receives n cpy 2

Fig. 15-13- 1 Meisis I Nndisjunctin (a) Nndisjunctin f hmlgus chrmsmes in meisis I (b) Nndisjunctin f sister chrmatids in meisis II Fig.

3 Fig Meisis I Nndisjunctin (a) Nndisjunctin f hmlgus chrmsmes in meisis I (b) Nndisjunctin f sister chrmatids in meisis II Fig Meisis I Nndisjunctin Meisis II Nndisjunctin (a) Nndisjunctin f hmlgus chrmsmes in meisis I (b) Nndisjunctin f sister chrmatids in meisis II Fig Meisis I Nndisjunctin Meisis II Nndisjunctin Gametes n + 1 n + 1 n 1 n 1 n + 1 n 1 n n (a) Nndisjunctin f hmlgus chrmsmes in meisis I Number f chrmsmes (b) Nndisjunctin f sister chrmatids in meisis II 3

Abnrmal Chrmsme Number Aneuplidy Results frm the fer6liza6n f

an abnrmal number f a par6cular chrmsme Mnsmic zygte Abnrmal Chrmsme

cpies f a par6cular chrmsme Chrmsme Number Plyplidy cndi6n in which

three sets f chrmsmes Tetraplidy (4n) is fur sets f chrmsmes cmmn in

4 Abnrmal Chrmsme Number Aneuplidy Results frm the fer6liza6n f gametes in which nndisjunc6n ccurred Offspring with this cndi6n have an abnrmal number f a par6cular chrmsme Mnsmic zygte Abnrmal Chrmsme Number has nly ne cpy f a par6cular chrmsme Trismic zygte has three cpies f a par6cular chrmsme Chrmsme Number Plyplidy cndi6n in which an rganism has mre than tw cmplete sets f chrmsmes Triplidy (3n) is three sets f chrmsmes Tetraplidy (4n) is fur sets f chrmsmes cmmn in plants but nt animals Plyplids are mre nrmal in appearance than aneuplids 4

Altera1ns f Chrmsme Structure Breakage f a chrmsme can lead t fur types f changes in chrmsme structure: (a) A B C D E A B C E Deletin 1.

Inversin reverses a segment within a chrmsme (d) A B C D E Reciprcal translcatin M N O C D E 4.

syndrme XXY male Sterile, small testes, sme female secndary sexual characteris6cs Mnsmy X, Turner syndrme X0 female sterile it is the nly knwn viable mnsmy in humans Structurally

5 Altera1ns f Chrmsme Structure Breakage f a chrmsme can lead t fur types f changes in chrmsme structure: (a) A B C D E A B C E Deletin 1. Dele1n remves a chrmsmal segment (b) A B C D E Duplicatin A B C B C D E 2. Duplica1n repeats a segment (c) A B C D E Inversin A D C B E 3. Inversin reverses a segment within a chrmsme (d) A B C D E Reciprcal translcatin M N O C D E 4. Translca1n mves a segment frm ne chrmsme t anther M N O P Q R A B P Q R Aneuplidy f Sex Chrmsmes Nndisjunc6n f sex chrmsmes Prduces a variety f aneuplid cndi6ns Klinefelter syndrme XXY male Sterile, small testes, sme female secndary sexual characteris6cs Mnsmy X, Turner syndrme X0 female sterile it is the nly knwn viable mnsmy in humans Structurally Altered Chrmsmes cri du chat ( cry f the cat ) specific dele6n in chrmsme 5 mental deficiencies catlike cry usually die in infancy r early childhd Translca6ns f chrmsmes Certain cancers, including chrnic myelgenus leukemia (CML) Nrmal chrmsme 9 Reciprcal translcatin Translcated chrmsme 9 Nrmal chrmsme 22 Translcated chrmsme 22 (Philadelphia chrmsme) 5

Excep1ns t the standard chrmsme thery Tw nrmal excep6ns t Mendelian gene6cs Sme genes lcated in the nucleus 2-3 dzen traits dependent upn gender f parent Genes lcated utside the nucleus Organelle

6 Excep1ns t the standard chrmsme thery Tw nrmal excep6ns t Mendelian gene6cs Sme genes lcated in the nucleus 2-3 dzen traits dependent upn gender f parent Genes lcated utside the nucleus Organelle genes Genmic imprin1ng Genmic Imprin1ng Varia6n in phentype depends n which parent passed alng the alleles fr thse traits Invlves the silencing f certain genes that are methylated during gamete prduc6n Fig Paternal chrmsme Maternal chrmsme Nrmal Igf2 allele is expressed Nrmal Igf2 allele is nt expressed Wild-type muse (nrmal size) (a) Hmzygte inherited frm mther inherited frm father Nrmal size muse (wild type) Dwarf muse (mutant) Nrmal Igf2 allele is expressed is expressed is nt expressed Nrmal Igf2 allele is nt expressed (b) Heterzygtes 6

Inheritance f Organelle Genes Extranuclear genes (r cytplasmic genes) genes fund in rganelles in the cytplasm Mitchndria, chlrplasts, and ther plant plas6ds carry small circular DNA mlecules

green plant Inheritance f Organelle Genes Sme defects in mitchndrial genes Prevent cells frm making enugh ATP And result in diseases that affect the muscular and nervus systems Fr example,

Explain why sex- linked diseases are mre cmmn in human males than females 3. Dis6nguish between sex- linked genes and linked genes 4. Explain hw meisis accunts fr recmbinant phentypes 5.

7 Inheritance f Organelle Genes Extranuclear genes (r cytplasmic genes) genes fund in rganelles in the cytplasm Mitchndria, chlrplasts, and ther plant plas6ds carry small circular DNA mlecules Extranuclear genes inherited maternally zygte s cytplasm cmes frm the egg The first evidence f extranuclear genes came frm studies n the inheritance f yellw r white patches n leaves f an therwise green plant Inheritance f Organelle Genes Sme defects in mitchndrial genes Prevent cells frm making enugh ATP And result in diseases that affect the muscular and nervus systems Fr example, mitchndrial mypathy and Leber s hereditary p6c neurpathy q Failure f xida6ve phsphryla6n Yu shuld nw be able t: 1. Explain the chrmsmal thery f inheritance and its discvery 2. Explain why sex- linked diseases are mre cmmn in human males than females 3. Dis6nguish between sex- linked genes and linked genes 4. Explain hw meisis accunts fr recmbinant phentypes 5. Explain hw linkage maps are cnstructed 6. Explain hw nndisjunc6n can lead t aneuplidy 7. Define trismy, triplidy, and plyplidy 8. Dis6nguish amng dele6ns, duplica6ns, inversins, and translca6ns 9. Explain genmic imprin6ng 10. Explain why extranuclear genes are nt inherited in a Mendelian fashin 7

BIOLOGY 101. CHAPTER 15: The Chromosomal Basis of Inheritance: Locating Genes Along Chromosomes

BIOLOGY 101. CHAPTER 15: The Chromosomal Basis of Inheritance: Locating Genes Along Chromosomes BIOLOGY 101 CHAPTER 15: The Chrmsmal Basis f Inheritance: Lcating Genes Alng Chrmsmes Lcating Genes Alng the Chrmsme CONCEPTS: 15.2 Sex-linked genes exhibit unique patterns f inheritance 15.3 Linked genes