Punnett square is a guide, but is not the end all be all of genetic inheritance. My apologizes if I.was incorrect in my wording of a very complex issue in a simple form, the fact still remains. Just because a person has natice american ancestory doesnt mean that they, themselves have any native american games at all.
What genetics researchers wanted to understand was the relationship between the “factors” for a trait passed on from parents and the trait as observed in offspring. Punnett explained it as a problem of trying to identify the traits of gametes while only being able to observe the traits of zygotes.
Gametes are sex cells such as sperm and eggs that only contain half of the “factors” or genes for trait that a zygote (full organism) contains. Gametes do not have observable traits because they remain single cells and there was no genetic sequencing in 1905. Punnett and Bateson knew that in sexual reproduction both parents contribute a gamete to the offspring, but some of their traits disappeared in one generation only to reappear in a later generation. Sometimes new traits appeared that were not observable in either parent. How could this be explained?
The first Punnett Square appeared in Mendelism described as a “chessboard”; they only took on Punnett’s name several decades later. What the chessboard allowed Punnett and Bateson to do was to predict what proportion of offspring would inherit a potential trait from their parents. When they bred generations of organisms they could then check the observed traits against their mathematical predictions.
Their experiments suggested that many traits are controlled by more than two “factors” and thus Punnett squares allowed them to keep track of complex combinations of ‘factors’ leading to different traits in offspring. Mendel’s experiments explained the inheritance of simple either/or traits fairly well but did not account for traits in which there were more possible options.
In its simplest form a Punnett square presumes that each trait is inherited separately; in fact we know this is not the case and so did Punnett and Bateson. (Some genes for specific traits are on the same chromosome and therefore usually inherited together.) Despite this, a Punnett square is still a useful tool for visualising the relationship between the traits of parents and the traits of their offspring.
The Punnett Square: predicting the traits of offspring based on the traits of their parents