Heredity
Why do children look like their parents? Why do brothers and sisters resemble each other? The secret is stored in the genes that are inherited from the parents. The genes incode the instructions that define our traits.

Where are these genes?

In most organisms, the genetic information is divided onto a few very long DNA threads. In humans, there are 46 DNA threads in each cell of the body. For lack of space – they can reach a length of up to one meter – the DNA threads are wound around a protein framework. A DNA thread together with its protein framework is called chromosome.

Thus a human being has 46 chromosomes. Of these, two are alike in shape and composition; the term 23 chromosome pairs is also used.

The only exceptions are the sperm and the ovum – altogether, these only contain 23 chromosomes.

When parents conceive a child, the father's sperm cell fuses with the mother' egg cell – thus, a cell with 46 chromosomes (23 chromosome pairs) emerges again. This cell will divide, ultimately developing into a child.

Some will resemble the mother, some will resemble the father, but the newborn offspring is never “a chip off the old block”, because aach parent has contributed one complete set of chromosomes to the child and, in this way, both parents have passed genes to the child.

Since the parents contribute chromosomes randomly to each child, every child receives a different combination of chromosomes. As a result, every child will inherit a unique combination of traits. Whether or not we have inherited mom’s slender build or dad’s tendency towards early baldness or whether grandpa’s short-sightedness has overleaped a generation, it is not until the fusion of the sperm and the egg cell that it is determined which genetic information we have received from previous generations.

 
 
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