Human Genome

Genome is haploid set of 23 chromosomes. It contains about 3 billions (3.000.000.000) bases (bp) and between 50 and 100 thousands genes. Besides structural genes that code RNA and polypeptides genome has many non-coding sequences of unknown function. They compose majority of our genome (about 97%).

The arrangement of genes is not even, some chromosomes contain more genes, other less. Some genes have many copies. The ones that are no longer functional are called pseudogenes.
They often have many deletions, mutations, lack of promotion or regulation regions. Many functional copies can quicken obtainment of product of the gene, but in eucariotic cells they are usually not used for simultaneous expression. They are activated in different life periods. For example genes coding for hemoglobin, protein made of 4 popypeptides: two so-called a chains and two b chains. In human body there are 5 copies of gene encoding b chain and 3 copies coding for a chain of hemoglobin molecule. Different copies for each chain undergo expression in different periods.

Non-coding sequences include repeats, introns, presudogenes. Repeats vary in longitude of repeated sequence and number of repeats. For example AC repeated from 10 to 60 times can be found after every about 30 000 nucleotides (30 kb). Very long repeats are characteristic for telomers and centromers. For human DNA repeating 5’CCCTAA3’ is characteristic for telomere region. There is a special enzymes – telomerase – that catalyze adding these sequences. Such ending enable distinguishing between normal and broken chromosomes. It prevents in some cases from random adding fragments of chromosomes.

Differences in DNA can occur in genes (alleles) as well as in non-coding sequences. Every person has a unique DNA. The differences are inherited. Taking advantage of DNA recombination methods it is possible to state with a very high probability rate (over 99%) the relationship or basing on little amount of DNA from blood, hair or sperm to identify the offender.