How Our Bodies Work

We can think of the human body and the cells that compose it as
a huge factory with millions of small plants to work closely together. Every cell (the ‘plants’ of the factory) has millions of tasks that need to be precisely coordinated. The cells are controlled by their nuclei, which gives the instructions. The instructions are encoded, they always reach the correct location within the cell,
and the encoded instruction is always carried out. The instruction says what kind of protein the cell needs to produce. Well, that’s a huge feat isn’t it?

Children inherit chromosomes from both pa-
rents. When the sperm cell and the egg cell unite, half of the chromo­somes of the fertilised egg comes from the father, and half from the mother. There are 23 pairs of chromosomes in the zygote: 22 pairs of body chromosomes (or auto­somes) and one pair of sex chromosomes (or allosomes).
Sex chromosomes determine whether the child
is a girl or a boy.

Chromosome

It consists of a condensed DNA chain and connected proteins. It forms during cell division.
There are a total of 23 pairs of chromo­somes in human cells. These con­tain the complete
genetic material of the cells.

DNA

A large molecule with a structure similar to a twisted ladder. This twisted ladder structure is called a double helix. DNA contains encod­ed instructions that are necessary for the cell to function.

Genes

In the double helix of the DNA, each ‘step’ is made up of a base pair. The order of these contains the encoded information. The 23 pairs of human chromosomes contain 3 billion base pairs. A section of the DNA that encodes a single protein is called a gene.

Chromosomes, DNA and genes

DNA molecules condense and form chromosomes. Each chromosome consists of a single DNA molecule, but the DNA molecules themselves consist of numerous genes. Genes encode the instruction given by the nucleus.