Copyright © 2005 Pearson Prentice Hall, Inc. Inheritance Patterns: Determined by Chromosome Movements in Meiosis 1 st Illustration:Down Syndrome –Trisomy 21, or Down Syndrome) (F12.19 p. 232) Nondisjunction at Meiosis I Down syndrome frequency increases with maternal age (F12.20 p. 233) –One of Many Caused by Abnormal Numbers of Autosomes

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Inheritance Patterns: Determined by Chromosome Movements in Meiosis 2 nd Illustration: Sex Determination –Human sex chromosomes (F12.8 p. 219) –Sex determination in mammals (F12.9 p. 219)

Copyright © 2005 Pearson Prentice Hall, Inc. X chromosome Y chromosome

Copyright © 2005 Pearson Prentice Hall, Inc. X1X1 X1X1 X2X2 X2X2 XmXm XmXm XmXm XmXm X1X1 X2X2 Y Y YYX1X1 X2X2 eggs female parent female offspring male offspring male parent sperm

Copyright © 2005 Pearson Prentice Hall, Inc. Inheritance Patterns: Determined by Chromosome Movements in Meiosis Some Genetic Disorders Are Caused by Abnormal Numbers of Sex Chromosomes –Effects of Nondisjunction of the Sex Chromosomes During Meiosis (T12.2 p. 230) Turner Syndrome (XO) Trisomy X (XXX) Klinefelter Syndrome (XXY) XYY Males –Medicinal plants (FE12.2 p. 231)

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Inheritance of Single Genes Illustration 1:Sex-Linked Genes –Found Only on the X or Only on the Y Chromosome Sex-linked: eye color in fruit flies (F12.10 p. 220) Some Sex-Linked Human Genetic Disorders –Color blindness, a sex-linked recessive trait (F12.17 p. 228) –Hemophilia among the royal families of Europe (F12.18 p. 229) –Dominant & Recessive Alleles –Homozygous & Heterozygous Individuals

Copyright © 2005 Pearson Prentice Hall, Inc. all the F 2 females have red eyes half the F 2 males have red eyes, half have white eyes XRXR XrXr XrXr XRXR r XRXR R R XrXr r Y Y XRXR R XRXR R eggs XRXR R XRXR R XrXr r XRXR R XRXR R Y XrXr r Y XRYXRY female parent female offspring male offspring male parent sperm

Copyright © 2005 Pearson Prentice Hall, Inc. Inheritance of Single Genes Some Human Genetic Disorders Are Caused by Dominant Alleles

Copyright © 2005 Pearson Prentice Hall, Inc. III IVIV ? ? or= colorblind = heterozygous carrier female, normal color vision or= normal color vision (not carrier) maternal grandfather motherfather sisterG. Audesirk T. Audesirk daughter aunts II I

Copyright © 2005 Pearson Prentice Hall, Inc. unaffected male unaffected female Edward Duke of Kent Victoria Princess of Saxe-Coburg Albert Prince of Saxe- Coburg-Gotha Victoria Queen of England Louis IV Grand Duke of Hesse-Darmstadt Alice Princess of Hesse Victoria Mary ElizabethAlexandra Tsarina FrederickErnest Mary Victoria Irene OlgaTatianaMariaAnastasia Alexis Tsarevitch Edward VII King of England Alexandra of Denmark Leopold Duke of Albany Helen Princess of Waldeck-Pyrmont Henry Prince of Battenburg Beatrice present British royal family (unaffected) Alexander Albert Alfonso XII Victoria Queen of Spain LeopoldMaurice Alfonso Crown Prince JuanBeatrice died in infancy MarieJaimeGonzalo carrier daughter and hemophiliac grandson several unaffected chidren carrier female hemophiliac male ? Nicholas II of Russia ??????? Copyright © 2004 Pearson Prentice Hall, Inc.

Copyright © 2005 Pearson Prentice Hall, Inc. Inheritance of Single Genes Explained by Mendel’s Laws Gregor Mendel (F12.1 p. 210) The relationships among genes, alleles, and chromosomes (F12.2 p. 210)

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chromosome 1 from tomato pair of homologous chromosomes

Copyright © 2005 Pearson Prentice Hall, Inc. Gregor Mendel: Laid the Foundation for Modern Genetics Doing It Right: The Secrets of Mendel’s Success –Flowers of the edible pea (F12.3 p. 211) –1st generation offspring of the flowering pea F1 (F1 p. 211) –2nd generation offspring of the flowering peaF2 (F 2 p. 212) –Homozygous parent P = Parental (F 3 p. 212) –Heterozygous parent (F 4 p. 212) –Homozygous allele distribution (F 5 p. 213) –Heterozygous 1st generation offspring allele distribution (F6 p. 213) –Heterozygous 2nd generation offspring allele distribution (F7 p. 213)

Copyright © 2005 Pearson Prentice Hall, Inc. intact pea flowerflower dissected to show reproductive structures

Copyright © 2005 Pearson Prentice Hall, Inc. true-breeding, purple-flowered plant true-breeding, white-flowered plant cross-fertilize pollen all purple-flowered plants Parental generation (P) First-generation offspring (F 1 ) Copyright © 2005 Pearson Prentice Hall, Inc.

3/4 purple 1/4 white Second- generation offspring (F 2 ) First- generation offspring (F 1 ) self-fertilize Copyright © 2005 Pearson Prentice Hall, Inc.

Inheritance of Single Traits Mendel’s Law of RANDOM SEGREGATION –THE 2 ALLELES OF A GENE “SEGREGATE” TO DIFFERENT GAMETES –Explains the Results of Mendel’s Crosses –Predicts the Outcome of New Types of Single-Trait Crosses –Inheritance of Dominant & Recessive Alleles on Homologous Chromosomes Determines the outcome of a single-trait cross (F12.4 p. 214) –Test cross (F8 p. 215)

Copyright © 2005 Pearson Prentice Hall, Inc. homozygous parent AAAA gametes

Copyright © 2005 Pearson Prentice Hall, Inc. PP P P purple parent all P sperm and eggs pp p white parent all p sperm and eggs p Copyright © 2005 Pearson Prentice Hall, Inc.

heterozygous parent AaaA gametes

Copyright © 2005 Pearson Prentice Hall, Inc. F 1 offspring p p PpPp PpPp spermeggs P P or

Copyright © 2005 Pearson Prentice Hall, Inc. ppp PpPp p p gametes from F 1 plants eggs F 2 offspring p P P P P PP sperm PpPp

Copyright © 2005 Pearson Prentice Hall, Inc. P p PP P p pp PpPp eggs Pp self-fertilize pPpP PPPP PpPpPp purple P P pPpP PpPp P ppp white spermeggs offspring genotypes genotypic ratio (1:2:1) phenotypic ratio (3:1) sperm

Copyright © 2005 Pearson Prentice Hall, Inc. all sperm p p P pp PpPp all eggs PP or Pp sperm unknown if PP if Pp egg pollen p P p 1212 all Pp sperm

Copyright © 2005 Pearson Prentice Hall, Inc. Inheritance of Single Traits: Multiple Traits on Different Chromosomes Mendel’s Law of INDEPENDENT ASSORTMENT –GENES ON DIFFERENT CHROMOSOMES ARE INHERITED INDEPENDENTLY –Traits of pea plants that Mendel studied (F12.5 p. 215) –Predicting genotypes and phenotypes for a cross between gametes that are heterozygous for two traits (F12.6 p. 216) –Independent assortment of alleles (F12.7 p. 217) –Heterozygous pea plant chromosomes (F9 p. 217) –Sweet pea at meiosis I (F10 p. 218) –Crossing over (F11 p. 218) –Sweet pea at anaphase I F12(p. 218) –Sweet pea at meiosis II (F13 p. 218)

Copyright © 2005 Pearson Prentice Hall, Inc. Seed shape Seed color Pod color Pod shape Flower color Flower location at leaf junctions at tips of branches tall (1.8 to 2 meters) dwarf (0.2 to 0.4 meters) Plant size smooth Dominant formTraitRecessive form wrinkled yellow inflated green white constricted purple

Copyright © 2005 Pearson Prentice Hall, Inc. SY SSYY SsYY ssYY ssyY SsyY SSYy SsYySsYy SsYySsYy ssyy SsyySSyy sSyYsSyYsSyy sSYY sSYy SSyY sYsY sYsY sy SySy SySy eggs self-fertilize seed shape seed color phenotypic ratio (9:3:3:1) smooth yellowsmooth yellow smooth green wrinkled yellow wrinkled green yellow green smooth wrinkled = = = = ssYy sperm x x x x Copyright © 2005 Pearson Prentice Hall, Inc.

S S ss s s Y S Y YY y yy S y independent assortment produces four equally likely allele combinations during meiosis SYsySysY meiosis II meiosis I S S S S s s s s Y Y Y Y y y y y chromosomes replicate S S ss Y Y y y replicated homologues pair during metaphase of meiosis I, orienting like this or like this pairs of alleles on homologous chromosomes in diploid cells S s Y y

Copyright © 2005 Pearson Prentice Hall, Inc How Are Genes Located on the Same Chromosome Inherited? Genes on the Same Chromosome Tend to Be Inherited Together Recombination Can Create New Combinations of Linked Alleles

Copyright © 2005 Pearson Prentice Hall, Inc. flower color gene pollen shape gene purple allele, P red allele, p long allele, L round allele, l

Copyright © 2005 Pearson Prentice Hall, Inc. flower color gene purple allele, P long allele, L red allele, pround allele, l pollen shape gene sister chromatids homologous chromosomes (duplicated) at meiosis I sister chromatids Copyright © 2005 Pearson Prentice Hall, Inc.

crossing over Copyright © 2005 Pearson Prentice Hall, Inc.

recombined chromatids P L p L P l p l Copyright © 2005 Pearson Prentice Hall, Inc.

PL p L Pl p l

12.6 Do the Mendelian Rules of Inheritance Apply to All Traits? Incomplete Dominance: The Phenotype of Heterozygotes Is Intermediate Between the Phenotypes of the Homozygotes –Figure Incomplete dominance (p. 221)

Copyright © 2005 Pearson Prentice Hall, Inc. RR eggs F2:F2: RR P: F1:F1: R R R RR R RR’ RR R’RR’R R sperm

Copyright © 2005 Pearson Prentice Hall, Inc Do the Mendelian Rules of Inheritance Apply to All Traits? A Single Gene May Have Multiple Alleles –Table 12.1 Human Blood Group Characteristics (p. 222) –Figure E12.1 Cystic fibrosis (p. 223)

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12.6 Do the Mendelian Rules of Inheritance Apply to All Traits? Many Traits Are Influenced by Several Genes –Figure Polygenic inheritance of grain color in wheat (p. 224)

Copyright © 2005 Pearson Prentice Hall, Inc. R1R1R2R2R1R1R2R2 eggs R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2 R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2 R1R1R2R2 R1R1R2R2 R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R2R2R1R1R2R2 R1R1R1R2R1R1R1R2 R1R1R2R2R1R1R2R2 sperm R1R2R1R2 R1R2R1R2 R1R2R1R2 R1R2R1R2 R1R2R1R2 R1R1R2R2R1R1R2R2 R1R2R1R2 R1R2R1R2 R1R2R1R2

Copyright © 2005 Pearson Prentice Hall, Inc Do the Mendelian Rules of Inheritance Apply to All Traits? Single Genes Typically Have Multiple Effects on Phenotype The Environment Influences the Expression of Genes –Figure Environmental influence on phenotype (p. 225)

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12.7 How Are Human Genetic Disorders Investigated? Figure Family pedigrees (p. 226)

Copyright © 2005 Pearson Prentice Hall, Inc. A pedigree for a dominant trait A pedigree for a recessive trait I II III I II III IV ???? ??? How to read pedigrees I, II, III = generations = male= female = parents = offspring or = shows trait or = does not show trait or = known carrier (heterozygote) for recessive trait or = cannot determine genotype from pedigree ??

Copyright © 2005 Pearson Prentice Hall, Inc How Are Human Disorders Caused by Single Genes Inherited? Some Human Genetic Disorders Are Caused by Recessive Alleles – Albinism Results from a Defect in Melanin Production Figure Albinism (p. 227)

Copyright © 2005 Pearson Prentice Hall, Inc. Human Rattlesnake Wallaby

Copyright © 2005 Pearson Prentice Hall, Inc How Are Human Disorders Caused by Single Genes Inherited? – Sickle-Cell Anemia Is Caused by a Defective Allele for Hemoglobin Synthesis Figure Sickle-cell anemia (p. 227)

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