En un experimento un floricultor cruzó plantas de flores púrpuras con plantas de flores blancas, los resultados obtenidos durante la primera generación fueron de un 100% de flores púrpuras, y en la segunda generación un 25% de flores serán de color blanco y el resto de color púrpura. Los genotipos de los parentales (P)

Los genotipos de los parentales son:

- pp (homicigota dominate con flores púrpura)

- bb (homocigota recesivo con flores blancas)  

Explanation:

Alelos:

p: púrpura y b: blanco

Genotipos parentales:  

- pp: homocigota dominante (flores púrpura)

- bb: homocigota recesivo (flores blanca)

Cruzamiento parental: pp X bb

F1: 100% pb  

Cruzamiento F1: pb X pb

F2: 25% pp (flores púrpuras), 50% pb (flores púrpuras) y 25% bb (flores blancas)

En este caso, el alelo que determina el color púrpura es dominante sobre el alelo que determina el color blanco. Es por esta razón que en la F1 todas las plantas heterocigotas exhiben un fenotipo con flores púrpura. En la F2 la proporción fenotípica será 1:2:1 (1 homocigota dominante, 2 heterocigotas y 1 homocigota recesivo), mientras que la proporción genotípica será 3:1 (3 plantas con flores púrpuras y 1 planta con flores blanca).

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.