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CHROMOSOME THEORY OF INHERITANCE

CHROMOSOME THEORY OF INHERITANCE. Proposed in 1902 by Walter Sutton and Theodor Boveri Noticed that transmission of chromosomes closely parallels Mendelian pattern Theory states: chromosomes are the carriers of the genes.

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CHROMOSOME THEORY OF INHERITANCE

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  1. CHROMOSOME THEORY OFINHERITANCE

  2. Proposed in 1902 by Walter Sutton and Theodor BoveriNoticed that transmission of chromosomes closely parallels Mendelian patternTheory states: chromosomes are the carriers of the genes

  3. Theory strongly supported after discovery of sex chromosomesFemale: homogameticMale: heterogametic

  4. Cruzamientos realizados por Morgan Parental femenino Parental masculino OJOS BLANCOS OJOS ROJOS Generación Parental F1: Toda de ojos rojos Conclusion: Ojo Blanco es recesivo

  5. Morgan’s eye-color crosses F1: All red-eyed Conclusion? White eye is recessive

  6. Cruzamientos realizados por Morgan Generación F1 Fenotipos F1 Ojos Rojos Ojos Rojos Resultados de la F2 1/2 Hembras ojo rojo : 1/4 machos ojo rojo : 1/4 machos ojo blanco Todas las hembras son de ojo rojo En base a este resultado Morgan propone que el carácter ojo blanco debe estar asociado al cromosoma X

  7. Morgan’s eye-color crosses What was going on? All the white-eyed flies were males! White-eyed flies have lower viability than wild-type

  8. Morgan’s eye-color crosses So, the ratio was probably really 3 : 1 On the basis of these results from crosses, Morgan proposed that w is on the X Hypothesized the following model as an explanation:

  9. Cruzamientos realizados por Morgan El macho tiene ojos blancos porque es hemicigoto. Muestra el fenotipo de un alelo recesivo en simple dosis Generación Parental Genotipo Parental diploide Gametos haploides

  10. Cruzamientos realizados por Morgan Gametos masculinos Generación F1 Gametos femeninos ½ w+/w (o X+/Xw) ½ w+/Y (o X+/Y) Genotipos F1 ½ hembras ½ machos Todos de ojos rojos Fenotipos F1

  11. Morgan’s eye-color crosses

  12. Morgan’s eye-color crosses

  13. Morgan’s eye-color crosses Morgan’s crosses showed a transmission pattern of: Male P to Female F1 to Male F2 This pattern is called crisscross inheritance It is indicative of X-linked recessives

  14. Morgan’s eye-color crossesReciprocal crosses:

  15. Morgan’s eye-color crosses

  16. Morgan’s eye-color crosses

  17. Morgan’s eye-color crosses

  18. Morgan’s eye-color crosses The difference in the phenotypic ratios in the 2 sets of crosses is because of the sex linkage

  19. Morgan’s eye-color crosses When the results of reciprocal crosses are not the same, Different ratios are seen for the sexes of the offspring Sex-linkage is strongly suspected

  20. Morgan’s results strongly supported the chromosome theory of inheritanceThe transmission pattern of the phenotypes neatly fit the pattern of the X chromosome

  21. The theory is further supported by the parallel behavior between Mendelian traits and chromosomes in meiosis:

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