Question

Define mendel's law of dominance and explain it with an example that is not always true?

Answer 1

Mendel's Law of Dominance can also be simply stated as: “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 thephenotype.”

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Answer 2

“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.”

What this means:

We all know that Mendel was breeding peas to observe the hereditary effects of different types of breeding.

In a cross of parents that are pure for contrasting traits:

Here pure means monohybrid whereas contrasting traits mean any two form a particular trait. For example, say height- Pea plant could be of two possible heights : either tall or short.

So, Mendel takes two pea plants: One short pea plant (thus having genes “tt” for expressing height) and one tall pea plant ( Having a genes “TT” which express or determine its height.)

Then he bred them by pollinating the flower of one monohybrid short pea plant with pollen of monohybrid tall pea plant. However, when he planted these seeds after harvesting, he found that all of the offspring plants were tall. Why was this so?

We all know that in sex gametes, genes break up and one of them forms a pair with an allelefrom the other cell. For pea plants, the two sets of gametes were TT and tt. Hence, during meiosis, the only possible combinations is Tt.