In humans, there are 23 chromosomes in each cell, and in each of those chromosomes, there are a hundred million bases included in average.
One strand of DNA is about 3.3 centimeters long, 2 nanometers (1 nanometer=1/1 million millimeter) in diameter. If this size were magnified so that the diameter were 10 centimeters, the length would become 3300 kilometers. When connecting all 23 chromosomes into one long strand, the length is 2 meters long. Before going on any further, you'll first have to know the difference between genes and DNA.
To understand more about DNA, you should go to the DNA section, but here also is a brief explanation. DNA stands for deoxyribonucleic acid. In one strand of DNA, is a encoded a pattern (ATGCGTCATCGGC...) to construct protein. You may think that one kind of protein is made from every strand of DNA, but actually different parts of the DNA make different types of protein, and together makes a bunch of various proteins.
Genes are a part of the DNA which make the proteins.
Also, DNA is roughly made of three parts.
1) Structral Gene: Gives orders on what kind of protein to make
2) Regulatory Gene: Gives orders on when and how much protein to make/ not to make.
The above two parts of the DNA combined, make genes.
3)The function of the third part is not yet completely known. Actually, this part takes up the most, from 90 to 95 percent of the whole DNA. The functions of genes have been clarified as in below.
At 1998 August present, 30 thousand out of 100 thousand human genes have been decoded. The functions of the human genes identified so far are as followed.
the appearance of genes and protein:22%
metabolism:17%
signals between cells:12%
immunity and homeostasis:12%
materials to construct and move cells:8%
cell division and synthesis of DNA:4%
non of the above categories:25%The function concerning the appearance of genes and protein take the biggest part- 22%. This part includes genes that order the sequence of amino acids, decide which genes should be transmitted, control the transcription from messenger ribonucleic acids (mRNA).
Next are the genes for metablism -17%. These genes encode enzymes for decomposing food to gain energy and building materials. Third, genes that send signals between cells to control hormones- 12%. Tied, are the genes of proteins for immunity and consistency of the body called homeostasis, which control the degree of body temperature, sweat, blood to live long life- 12%. Then comes the genes to construct and move cells- 8%.