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Hard to Predict What Will Happen

The 32 pairs of chromosomes inherited by offspring can be inherited from either parent and in any random combination so each offspring has its own unique identity (unless an identical twin from a single egg). As already mentioned when genetic recombination takes place a special type of cell division takes place during the formation of sperm and egg cells that gives them the correct number of chromosomes. Each has only half the number of chromosomes other body cells have. Inside the cells that produce sperm and egg cells, chromosomes become paired and each may swap a portion of its genetic material for the matching portion of its mate. After this crossover occurs the chromosomes separate and are parceled out into individual sex cells. Each of the chromosomes moves independently of the others. So what chromosome of one pair is inherited doesnít influence what copy of the other 32 pairs is inherited.

So any egg or sperm, the gametes, receive one of 2 possible chromosomes 32 times (the total number of possibilities is 2 raised to the 32nd power) or more than 1,589 million possibilities.

This recombination of genes makes it impossible to predict the outcome of any given mating and until more genetic markers have been identified pedigree charts using the rules of inheritance is the only way of planning matings.

There is a misconception is that genes alter from one generation to the next. This is simply not the case. The particular characteristic is either expressed in the individual or recessive. Remember Mendel and his peas and Thomas and his fruit flies.

What does alter though is the overall genetic base as the 32 pairs of chromosomes could be inherited from either parent in random combination. Each new individual is unique and involves a random recombination of its parents. Hence two siblings can be unlike e.g. Sadlerís Wells and Fairy King. It is important to recognize that every individual is unique and represent a combination of genes that have never been together before in that particular combination. With humans the number of potential pedigrees before a repeat is necessary has been estimated at 10^477. This is somewhere between a number I cannot imagine and infinity. I have heard the figure 300 billion mentioned.

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