Gallery for genetics genius. A new exhibition commemorates the 19th Centuiry work of Gregor Mendel,
the "father of genetics". [BBC News: sci/tech] Gregor Mendel was a great scientist and did found the discipline of genetics. What many people don't know is that his data as reported in his papers is now known to be nearly impossible to obtain. Here is a long explanation, but you may find it amusing.
First some background so you can understand the cheat. Many of the traits that he was studying in plants separated on a 3 to 1 ratio or a 1 to 1 ratio. A similar example I can give you that you are probably familiar with is that of brown eyes versus blue eyes. If two brown-eyed people have a child, it will most likely be brown eyed. If blue-eyed and brown-eyed couples have children, they often all have brown eyes. If two blue-eyed people have children, they will have blue eyes. It is said in genetics that brown eyes are dominant over blue eyes.
Of course it is not that simple, nothing ever is. We actually have two copies of each allele that determines eye color. So it is possible for a brown-eyed person to contain one allele for blue eyes and one allele for brown eyes. Their eyes are brown because the brown-eyed gene is dominant. This type of person is described as heterozygous for eye color. Someone who has two of the same allele (two brown-eyed alleles or two blue-eyed alleles) is called homozygous. When we mate, only one copy of each allele is passed down to our offspring, with the other copy coming from our partner. Now if a heterozygous brown-eyed person has a child with a homozygous blue-eyed person (they have to be homozygous to be blue-eyed because it is a recessive allele), then half the children will have blue eyes and half will have brown eyes. Here is another example. If a heterozygous brown-eyed person has a child with a heterozygous brown-eyed person then 3 out of 4 children will be brown-eyed, but 1 of 4 will be blue-eyed. The three children received at least one brown-eyed allele from their parents, but one child received both blue-eyed alleles. So in various crosses you can get statistical ratios and you can predict what is going to happen in any cross once you figure out what allele is dominant. These, in a nutshell, are the ideas that Gregor Mendal discovered.
Much later scientists learned that DNA was the heredity material and they also learned that during the separation of the chromosomes during meiosis to make gametes (eggs and sperm for mammals) there is a low frequency of DNA exchange between chromosomes. What this can mean is that the alleles may swap places. For our purposes this means that this perfect ratio of 1 to 1 or 3 to 1 will be a bit off. Now when you look at Gregor Mendels reported data you find that it is too perfect. With the DNA exchange going on between chromosomes he could not have possibly gotten those numbers. This must have bothered him, so he fudged the data (just a little bit) to make it fit his theories. The take home message is, even if your model does not explain the data perfectly, don not fudge the data. There is probably a good reason for it.
1:00:30 PM 
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