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Mendels Law of Dominance - The first law of Mendel states that In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.

Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

While Mendel was crossing (reproducing) his pea plants (over and over and over again), he noticed something interesting.

When he crossed pure tall plants with pure short plants, all the new pea plants (referred to as the F1 generation) were tall.

Similarly, crossing pure yellow seeded pea plants and pure green seeded pea plants produced an F1 generation of all yellow seeded pea plants.

The same was true for other pea traits. So, what he noticed was that when the parent plants had contrasting forms of a trait (tall vs short, green vs yellow, etc.) the phenotypes of the offspring resembled only one of the parent plants with respect to that trait .

So, Mendel proposed a law in which he proposed that There is a factor that makes pea plants tall, and another factor that makes pea plants short.

Furthermore, when the factors were mixed, the tall factor seemed to dominate over the short factor.

Now, from our modem wisdom, we use allele or gene instead of what Mendel called factors. There is a gene in the DNA of pea plants that controls plant height (makes them either tall or short).

One form of the gene (allele) codes for tall, and the other allele for plant height codes for short.

For abbreviations, we use the capital T for the dominant tall allele, and the lowercase t for the recessive short allele.

 
 

 
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