DNA Basics

Every living cell on earth has DNA to reproduce. DNA in the nucleus of the cell provides a blueprint of the entire living organism. DNA contains the framework and coding to “rebuild” not just the cell as it divides, but has the details necessary to life for the next “generation”. For those unfamiliar with DNA, the website, DNA from the Beginning can provide the background to understand the mechanisms of living reproduction.

Chromosomes are “colored bodies” — cell structures which are strongly stained by a selection of colorful dyes used in research; the word comes from the Greek, chroma (color) and soma (body). Each chromosome is made of protein  and a single molecule of deoxyribonucleic acid (DNA). A gene is a segment of DNA that is passed down from parents to children and confers a trait to the offspring. Genes are organized and packaged in units called “chromosomes.”  Humans have 23 pairs of chromosomes. One set of chromosomes for each pair comes from a person’s mother, and the other set of chromosomes comes from the father. Certain genetic traits are linked to a person’s sex and are passed on through the sex chromosomes: The x-chromosome (Mitochondria) is provided by the female; the x-chromosome is provided by the male.

Base pairs are the building blocks of DNA create the pattern of the specific details of the gene. In the human female, the mitochondria contains 154,913,754 base pairs while the male y-chromosome contains 57,741,652 base pairs. In normal humans, there is at least one x-chromosome: In females there are two; in males, there is one y-chromosome and one x-chromosome. The sex chromosomes are named ‘x’ and ‘y’ because of their appearance under magnification.

The entirety of human DNA has been ‘mapped’; those who want to learn more may see The Human Genome Project Video. Further research has shown the migration of classified groups of people through ‘haplogroups‘ —  those sharing a common ancestor,  having the same Single Nucleotide Polymorphism (SNP) mutation. Haplogroups are assigned letters of the alphabet, and refinements consist of additional number and letter combinations. The human haplogroup Y-chromosome (Y-DNA) is passed solely  along the patralineal line from father to son, while the X-chromosome midochondria (mtDNA) is passed solely along matralineal lines from the mother to the children. Neither recombines so Y-DNA and mtDNA change only by chance mutation at each generation with no intermixture between parents’ genetic material: Haplogroups can remain stable for thousands of years — SNP testing can determine whether people have common ancestors or not.