| TekstiThis property is a special property in this wiki.
|
<P align="justify"> DNA research (de … <P align="justify"> DNA research (deoxyribonucleic acid) is a long molecular structure containing genetic code that was explicated in 1953. This breakthrough in molecular biology was of great significance for population genetics and associated applied sciences. DNA is a long molecule consisting of nucleotides. Each nucleotide contains a deoxyribose sugar molecule, phosphate and a base. The nucleotides differ from one another in terms of their base, of which there are four types: adenine (A), thymine (T), guanine (G) and cytosine (C). Since the nucleotides differ from each other purely in terms of their base, the DNA sequence is a chain formed of these bases (for example: A-T-G-T-C-A-G-). </P>
<P align="justify"> The nucleotides form a double helix composed of two long strands in which the sugar of one nucleotide bonds with the phosphate of the next. The DNA of the human cell nucleus consists of strands of about 3.4 billion base pairs. The strands are attached to one another by bonds between the bases according to the base pairing rule: adenine bonds with thymine, and guanine with cytosine. Most of a human being s DNA is located in the chromosomes of the cell nucleus in the form of loops (chromatins) around the protein particles of the chromosome. A human being has 23 pairs of chromosomes, that is 46 chromosomes in all. One of the pairs constitutes the sex chromosome (the female has two X chromosomes, the male one X and one Y chromosome), and the rest are so-called autosomes. Since one member of the pairs of chromosomes is inherited from the mother and one from the father, an individual inherits the DNA of both parents. Y chromosomal DNA (Y-DNA) is only inherited from father to son because only men have the Y chromosome. We can thus use Y-DNA to investigate the history of our male ancestors. About 1% of a cell s DNA is located outside the cell nucleus in the mitochondria of the cytoplasm which are responsible for the production of energy in the cell. Human mitochondrial DNA (mtDNA) consists of a helical molecule of 16,569 self-replicating base pairs. MtDNA is inherited by children (both boys and girls) from their mothers. It is believed that men cannot pass on the mtDNA they have inherited from their mothers to their children because the mitochondria of the sperm cell (and thus its mtDNA) remain outside the fertilized ovum (zygote). We can therefore investigate the history of our female ancestors by studying mtDNA.</P>
<P align="justify"> Genes (of which human beings possess 30,000 40,000) are DNA sequences that contain a code of the kind of enzyme or structural protein that is to be reproduced, thus determining hereditary traits, and consequently the phenotypes of an individual. A phenotype may be a morphological feature, a physical characteristic or a serological property (such as a blood group, an enzyme or a protein). Each gene has a fixed place (locus) in the chromosome. </P>
<P align="justify"> Over 90% of DNA does not carry genetic information and is made up of repeated base sequences. The length of these so-called tandem copies (for example C-A-C-A-C-A, etc.) varies from two base pairs to over two thousand. They are variously called microsatellites, minisatellites or satellite DNA.</P>
<P align="justify"> There are differences between the DNA sequences of individuals, populations and species. These differences have originally come about as a result of mutations and have been passed on to succeeding generation by reproductive cells (gametes). The majority of the mutations do not affect the genotype because most of the DNA does not carry genetic coding. Some mutations have a harmful effect, while a small number of them are adaptive. The latter enhance an individual s fitness, i.e. his or her likelihood of living for a long time and reproducing. Natural selection leads to the expansion of such new adaptive alleles (variant genes) over the generations.</P>
<P align="justify"> The extremely rapid development of molecular technology and genetic engineering in the 1980s has increased out knowledge of genomes (the genetic make-up of an individual and/or a species). Thanks to this, the sum of our knowledge about genes, their number and function, has increased. Now it is also possible to isolate and study DNA even from partly fossilized bones that are several tens of thousands of years old. </P>
[[Saami in the light of population genetics|Population genetics]] <BR>
[[Molecular anthropology|Molecular anthropology]]<BR><BR>
[[Table of contents: Demography, ethnicity and physical anthropology| Table of contents: Demography, ethnicity and physical anthropology]]<BR><BR>hysical anthropology]]<BR><BR> +
|
