Crowe Genealogy Ireland and the World Pic 1

Why are Children Different to Parents?

Genetics is simple mechanics and yet when you combine a lot of simple things together it can look very complicated and trying to understand it is difficult. Here are a few simple concepts to give you a base to work from.

First of all there are chromosomes, twisted bundles of long thin DNA - imagine them as balls of wool? They come in pairs, both chromosomes in a pair can do the same kinds of chemistry. Usually only one chromosome is working or operational.

Humans have 22 pairs of chromosomes and one pair that is not identical, the X and the Y chroosomes that determine the sex of the person. In the diagram below only 6 pairs of chromosomes are shown to make it easier to understand.

So normally the chromosomes are working and can not be seen as they are uncoiled and spread about like a pan of spaghetti. They only become coiled up and packaged when the cell is going to divide. When sex cells are made (egg and sperm in humans) the division causes one of each pair to be pulled to opposite ends of the cell. Which one of the pair goes one way and which goes the other way is random. Now each sex cell has half the chromosomes needed for a new human. When egg and sperm combine to make an embryo there are 23 pairs again. This time half from mum and half from dad.


For each of the children they each have 6 boxes and 6 circles - 6 pairs of chromosomes. However they may have white shapes or coloured shapes - this is a random collection of four grandparents chromosomes! They are very different to their parents and each other! 

Each grandparent has only contributed about 25% of their DNA to their grandchildren. This mixing of DNA is essential to the healthy working of chromosomes and was understood by the ancients despite knowing the mechanics. Inbreeding in animals is a clear example of what may happen if close cousins were to marry.This is only one reason why intended marriages were given public notice (as to 'just cause and impediment') that may bring problems for children.

Some ancient societies believed that marrying within the family clan would conserve the 'special genetics' of the 'royal divinity' and keep the 'strength' of the family without being diluted by ordinary people! They perhaps, needed to be 'kissing cousins' though and not brothers and sisters!


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