Hiding genes - the mystery of black and white genetics
What is genetics?
Genetics - according to Wikipedia - means: "a discipline of biology, the science of heredity and variation in living organisms."
Genetics is the main forming power of our behaviour and appearance, since genetics plays a huge role in the process of inheritance and in the development of mankind and all organisms. The whole modern, mid-nineteenth century view began with the work of Gregor Johann Mendel, a great scientist born in the Austrian Empire (now Czech Republic). He was the first scientist who observed that all organisms inherit certain traits from their parents via genes. Ha made many experiments with plants, and he collected all of his ideas and experiences in a book called "Experiments on Plant Hybridization".
The Punnett-square is a special squared diagram for genetical crosses and/or breeding experiments. The diagram predicts the possible outcomes of a particular cross.
On the first picture on the right you can see the possible outcomes of crossing two pea plants - the inheritance of the dominant purple and the recessive white flowers.
Meanwhile, on the second picture you can see the cross of a heterozygous (yellow) pea and a recessive gene carrier (green) pea. As you can notice, inheritance of traits depends on the traits of both parents.
Black couple with a white child and a white couple with a black baby?
On the 20th of July, in 2010 an interesting article appeared in the news all over the world: a black couple gave birth to a white girl with blonde hair and sparkling blue eyes. At first, most of the people would think that this is impossible, maybe the mom of the little baby cheated on her husband 9 months before the girl was born and most of them would also do a DNA test to get to know the truth. In fact, the truth is that this can happen to anyone who have mixed genes and have white ancestors.
The more white or black genes the parents have in their DNA the more likely they will give birth to a child who has different skin color. So it is possible that the mother never cheated on the father and they still have a child of different skin color.
Keeping in mind that skin color is neither dominant nor recessive I also have to state that if the parents have different skin complexion, like the black parent has no white ancestor and the white parent has no black ancestor either, they will have a child who has a "mixed" color of black and white or can look mostly white with some black features (like dark hair and eyes).
I also would like to add that skin color is believed to be determined by seven different genes. If a woman or a man is of a mixed race, their genes contain a mixture of black and white traits. When they come together, they will have a mixed-race baby.
But occasionally the egg or the sperm can contain genes coding for only one color. If two come together that contain the same color - for example an egg with white and a sperm with also white coding - the child will have a different skin color than their parents - in our example that would result in a white child of black parents.
Twins with different skin color
This case is also possible naturally, if two eggs are released in the mother and are fertilized by two different sperms (that have different coding).
On the other hand, in this case it is also possible that the mother was cheating on the father with a different colored man - but only when neither parents have mixed ancestry. It happened years ago, when a white couple gave birth to twins - one white and one black child. As it turned out, the reason for the twins was that the mother was cheating on the father with a black guy - one egg was fertilised by the sperm of the father and another was fertilised by the sperm of the lover... I think they divorced soon after this whole story came into light.
In IVF (in-vitro fertilization) cases this is also possible. In 2002 there was a couple from Holland, who gave birth to twins who had different skin color. No, the mother never cheated on the father - the fact is that in the lab, during the infertility treatment the sperms of the father were accidentally mixed with the sperms of another, black man. And after these were the eggs of the mother fertilised. Big mistake, but it can happen.
Last but not least, I also have to mention mutation. Mutation - when there is a random change in the DNA sequence of a cell - can also cause different skin color, but it is extra rare of course.
In fact, we should never forget that the laws of genetics are very complicated and we cannot never fully understand all of them.
Books about genetics
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© Copyright 2012-2014, Zsofia Koszegi-Nagy (zsobig)
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