Chromosomes and traits

All creatures have inherited properties from their ancestors. You too. You have inherited properties from your parents. Maybe your nose look just like your dad's? Maybe you have curly hair, just like your mum?

When you start to look, you'll find plenty of characteristics that you and one of your parents have in common. So, some way, your body learned how it was to develop and look. That information came from your parents. And it must have been there even before you were born, in the very first cell that was about to become your body. Something in that cell carried information about you.

Here is the cell. There, in the cell nucleus, there is a tangle of a twisted rope-ladders. They consist of a substance called DNA. There, in the DNA, we find the information. That's it.

All information about the inherited traits, or the genes, exists in a few long twisted rope-ladders called DNA. -- Something happens. The DNA is sorted in chromosomes, that organise themselves. They line up, and the cell -- divides. And those rope-ladders are now present in both cells. They were copied, when the cell divided.

So, we now have two cells with identical rope-ladders in the nucleus. Every time the cells divide, the chromosomes are copied. Today, your body is built of many billions of cells, and in almost everybody, there are identical chromosomes. So, the genes, carrying information about you, are present in all cells in your body. And it's the same for every organism.

Every single one. The chimpanzee, the white shark, the blackbird or the wild rose. They all have chromosomes in the cells that carry information about how they will develop. The closer two organisms are related, the more similar are their genes. You and your siblings are closely related and look like each other.

You have a lot of genes in common. The more remotely you are related, the more the chromosomes differ, in number and composition. In almost all human cells, there are 46 chromosomes. Chimpanzees have 48 chromosomes in each cell. They are similar to human chromosomes in many ways, and this is why we can see so many similarities between chimpanzees and humans.

Wild roses don't look like humans or chimpanzees. And if we look, we find only 14 chromosomes in each cell, and they make the plant develop stems, leaves, thorns and flowers. The genes of the rose differ a lot from the human's, and hence the two species are very distantly related. This is a foundation for all life, and for how traits are inherited. The DNA-molecules, the chromosomes, are copied when the cells divide, and the genes are passed on from generation to generation.

The genes control your development - from one single cell to a body with brain and lungs and legs and arms. You have received the genes from your parents. They got their genes from their parents. The closer the relationship, the more similar the genes. --