Definition of genes
Gene is a stretch of DNA with a specific function, which is during cell division able to create its own identical copies transmitted to future generations. Each chromosome contains thousands of genes, each of which is long thousands of bases.
The human body contains 46 chromosomes in 23 pairs. For each pair, one is inherited from the mother and one from the father. 22 pairs of chromosomes are identical in males and females; these are called autosomes. The remaining two chromosomes are called sex chromosomes and are called X and Y. The female offspring will inherit one X chromosome always from its mother, so what sex the offspring will be, it depends entirely on the man. If sperm delivers the X chromosome, then the baby will be a girl. the female sex, if Y, it will be a son.
We have two copies of each chromosome and chromosomes keep our genes, hence we have two copies (alleles) of every gene, which is contained in the autosomes.
Meaning of genes
The results of the Human Genome Project specify the number of genes in the human genome at 30 000 to 40 000. In any gene string base contains instructions for the formation of individual proteins and any protein comprises a specific function of the human body. This protein may then be for example an enzyme, structural protein or marker protein. For example, some enzymes are important in the digestion of food; structural proteins give shape to our cells and signaling molecules allow cells to communicate with each other. Each gene contains a signal sequence of bases that provide information cells about which gene should be used to fulfill that function. These sequences may for example comprise instructions for causing the protein responsible for the growth of hair only in cells of the skin of our head, not in every cell of the body.