CHROMOSOME THEORY OF INHERITANCE. Proposed in 1902 by Walter Sutton and Theodor Boveri Noticed that transmission of chromosomes closely parallels Mendelian.

Presentación del tema: "CHROMOSOME THEORY OF INHERITANCE. Proposed in 1902 by Walter Sutton and Theodor Boveri Noticed that transmission of chromosomes closely parallels Mendelian."— Transcripción de la presentación:

1 CHROMOSOME THEORY OF INHERITANCE

2 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

3 Theory strongly supported after discovery of sex chromosomes Female: homogametic Male: heterogametic

4 Cruzamientos realizados por Morgan F 1 : Toda de ojos rojos Conclusion: Ojo Blanco es recesivo Generación Parental Parental femeninoParental masculino OJOS ROJOS OJOS BLANCOS

5 Morgan’s eye-color crosses F 1 : All red-eyed Conclusion? White eye is recessive

6 Resultados de la F 2 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 Cruzamientos realizados por Morgan Generación F1 Fenotipos F1 Ojos Rojos Ojos Rojos

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

10 Cruzamientos realizados por Morgan Gametos masculinos Gametos femeninos Generación F1 Genotipos F 1 ½ w + /w (o X + /X w ) ½ w + /Y (o X + /Y) Fenotipos F 1 ½ hembras ½ machos Todos de ojos rojos

11 Morgan’s eye-color crosses

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13 Morgan’s crosses showed a transmission pattern of: Male P to Female F 1 to Male F 2 This pattern is called crisscross inheritance It is indicative of X-linked recessives

14 Morgan’s eye-color crosses Reciprocal crosses:

15 Morgan’s eye-color crosses

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18 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 inheritance The 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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