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P Generation

P Generation. Yellow-round seeds ( YYRR ). Green-wrinkled seeds ( yyrr ). y. Y. r. . R. r. R. Y. y. Meiosis. Fertilization. r. y. Y. R. Gametes. All F 1 plants produce yellow-round seeds ( YyRr ). F 1 Generation. R. R. y. y. r. r. Y. Y. LAW OF SEGREGATION

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P Generation

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  1. P Generation Yellow-round seeds (YYRR) Green-wrinkled seeds (yyrr) y Y r  R r R Y y Meiosis Fertilization r y Y R Gametes All F1 plants produce yellow-round seeds (YyRr) F1 Generation R R y y r r Y Y LAW OF SEGREGATION The two alleles for each gene separate during gamete formation. LAW OF INDEPENDENT ASSORTMENT Alleles of genes on nonhomologous chromosomes assort independently during gamete formation. Meiosis r r R R Metaphase I y Y y Y 1 1 r r R R Anaphase I Y y Y y Metaphase II r R R r 2 2 y Y y Y y Y Y y Y y y Y Gametes r R r r R r R R 1/4 1/4 1/4 1/4 yr yR YR Yr F2 Generation An F1  F1 cross-fertilization 3 3 : 1 : 3 9 : 3

  2. 0.5 mm Parent Bud

  3. EXPERIMENT P  Generation F1 All offspring had red eyes Generation RESULTS F2 Generation CONCLUSION + P w w X X  Generation X Y + w w Sperm Eggs + + F1 w w + Generation w w + w Sperm Eggs + + w w + F2 w Generation + w w w w + w

  4. X Y

  5. 44 + XX 44 + XY Parents 22 + X 22 + X 22 + Y or + Sperm Egg 44 + XX 44 + XY or Zygotes (offspring) (a) The X-Y system 22 + XX 22 + X (b) The X-0 system 76 + ZW 76 + ZZ (c) The Z-W system 32 (Diploid) 16 (Haploid) (d) The haplo-diploid system

  6. XnY XnY XNXN XNXn  XNY XNXn   Sperm Sperm Sperm Xn Y XN Xn Y Y Eggs Eggs XNXN Eggs XNXn XNY XN XNY XN XNXn XNY XN XnXn XnY XNXn XNY XnXN XnY Xn Xn XN (a) (b) (c)

  7. X chromosomes Allele for orange fur Early embryo: Allele for black fur Cell division and X chromosome inactivation Two cell populations in adult cat: Active X Inactive X Active X Black fur Orange fur

  8. EXPERIMENT P Generation (homozygous) Wild type (gray body, normal wings) Double mutant (black body, vestigial wings)  b b vg vg b+ b+ vg+ vg+ F1 dihybrid (wild type) Double mutant TESTCROSS  b+ b vg+ vg b b vg vg Testcross offspring b+ vg+ b vg b+ vg b vg+ Eggs Black- normal Wild type (gray-normal) Black- vestigial Gray- vestigial b vg Sperm b b vg+ vg b+ b vg+ vg b b vg vg b+ b vg vg PREDICTED RATIOS 1 If genes are located on different chromosomes: 1 : : : 1 1 If genes are located on the same chromosome and parental alleles are always inherited together: 1 0 : 1 : 0 : 965 : : 185 : 944 206 RESULTS

  9. Testcross parents Gray body, normal wings (F1 dihybrid) Black body, vestigial wings (double mutant) bvg b+vg+ bvg b vg Replication of chromo- somes Replication of chromo- somes b+vg+ bvg b+vg+ bvg bvg bvg bvg bvg Meiosis I b+vg+ Meiosis I and II b+vg bvg+ bvg Meiosis II Recombinant chromosomes bvg bvg+ b+vg b+vg+ Eggs Testcross offspring 965 Wild type (gray-normal) 944 Black- vestigial 206 Gray- vestigial 185 Black- normal bvg b+vg+ bvg b+vg bvg+ bvg bvg bvg bvg Sperm Parental-type offspring Recombinant offspring 391 recombinants Recombination frequency  100 = 17% = 2,300 total offspring

  10. RESULTS Recombination frequencies 9% 9.5% Chromosome 17% b cn vg

  11. Mutant phenotypes Short aristae Cinnabar eyes Vestigial wings Brown eyes Black body 0 48.5 57.5 67.0 104.5 Gray body Red eyes Normal wings Red eyes Long aristae (appendages on head) Wild-type phenotypes

  12. Meiosis I Nondisjunction Meiosis II Nondisjunction Gametes n – 1 n + 1 n – 1 n n n + 1 n + 1 n – 1 Number of chromosomes (b) Nondisjunction of sister chromatids in meiosis II (a) Nondisjunction of homologous chromosomes in meiosis I

  13. A B C D E F G H A B C E F G H Deletion (a) A B C D E F G H A B C B C D E F G H Duplication (b) A B C D E F G H A D C B E F G H Inversion (c) A B C D E F G H M N O C D E F G H (d) Reciprocal translocation M N O P Q R A B P Q R

  14. Reciprocal translocation Normal chromosome 9 Translocated chromosome 9 Translocated chromosome 22 (Philadelphia chromosome) Normal chromosome 22

  15. Normal Igf2 allele is expressed Paternal chromosome Maternal chromosome Normal Igf2 allele is not expressed Wild-type mouse (normal size) (a) Homozygote Mutant Igf2 allele inherited from mother Mutant Igf2 allele inherited from father Normal size mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed Mutant Igf2 allele is expressed Mutant Igf2 allele is not expressed Normal Igf2 allele is not expressed (b) Heterozygotes

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