Mendels laws

Mendel examined clear-cut dichotomous characteristics such as smooth versus wrinkled coats in peas. He first noted that when parents of different types were crossed, the first generation (F1) offspring displayed uniformity of that characteristic. He inferred that this uniformity was due to one phenotype being dominant and the other being recessive. Thus, when homozygous parents AA and aa produced heterozygote Aa offspring, these offspring displayed the phenotype of the AA parent rather than manifesting a phenotype intermediate to those of both parents.

Mendel then demonstrated that when the F1 heterozygotes (Aa) were intercrossed (Aa * Aa), segregation resulted in the second F2 generation showing recessive and dominant phenotypes in the ratio of 1 to 3. He then inferred that this F2 generation consisted of three types (AA, Aa, and aA, aa) occurring with a probability of 1 : 2 : 1.

Finally, Mendel showed that when the transmission of two different phenotypic traits was studied, they showed independent assortment. We now know that independent assortment occurs when the genes coding for these traits are either located far apart on the same chromosome or are on different chromosomes (see linkage).

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