* Talk about what makes the colour of the eye appear and how it works Body
* Explain dominant colours
* Give examples of how the colours and genes work with different eye colour parents Finish
* Talk about how eye colours change and what makes them change
Is there any possible way for two blue-eyed parents to have a green or brown-eyed child? Eye colour comes from a combination of two black and yellow pigments called melanin in the iris of your eye. If you have no melanin in the front part of your iris, you have blue eyes. An increasing proportion of the yellow melanin, in combination with the black melanin, results in shades of colours between brown and blue, including green and hazel. The best way to illustrate how this might happen is with an example. Let's say there is a genetic pathway made up of four genes (cleverly named A, B, C, and D) that are needed to make brown eyes. A mutation in both copies of any one of these genes results in blue eyes (these mutations are denoted with lower case letters, a, b, c, and d). Now let's say that dad has blue eyes because of a mutation in both his copies of gene A and mom because of a mutation in both her copies of gene D. As I am sure you know, we have two copies of each gene, one from our mom and one from our dad. If either parent gives you a brown version of a gene, it will be dominant over the blue copy. Let's suppose that mom gives you a brown copy of gene A and dad gives you a brown copy of gene D. What colour eyes would you have? Brown.(The same argument works for green eyes as well.) Another common genetic process that could be responsible for brown eyes from blue-eyed parents is called recombination. When eggs and sperm are made, only one of a pair of chromosomes gets put into an egg or sperm. Before this happens, there is a bunch of DNA swapping that goes on between the pair of chromosomes. Sometimes when the DNA is swapped or...
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