This section is concerned with introducing common genetic terms and applying genetics into the current English population. To begin with I would like to look at chromosomes and then move on to look at other terms used in genetic genealogy.

Adeline (A), hymine (T), guanine (G) and cytosine (C) are the four bases or building blocks that make up DNA.

An Allele is a DNA sequence that repeats at a certain place or locus on the chromosome. The Allele value is the number of times the sequence repeats. For example, if we look at the DYS (DNA Y-chromosome Segment) marker 393, we see that the DNA sequence AGAT is repeated. In my case the AGAT sequence is repeated 13 times giving me an Allele value of 13.

Cambridge Reference Sequence (CRS) is the mitochondrial DNA first sequenced in 1981 which is used as a basis for comparison with mtDNA test results.

Chromosomes are basically long segments of DNA. They are found in the nucleus of cells and there are 46 in human nucleus.

DNA or Deoxyribonucleic acid is a chemical which contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main function of the DNA molecule is the long-term storage of information. DNA is frequently compared to a set of blueprints or a recipe, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. DNA segments that carry this genetic information are called genes. At the DNA level all human beings are 99.9 percent identical. Each person's individuality come from the 0.1 percent of the DNA which is different. There are four types of DNA: Autosomol DNA; X Chromosome DNA; Y Chromosome DNA; and Mitochondrial DNA. When DNA is analysed some sections of the DNA called Markers are analysed in detail. If two people have 34/37 to 37/37 markers and the same surname then they are related in the time that public records have existed.

Genes are the basic units of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cells and pass genetic traits to offspring. In general terms, a gene is a segment of nucleic acid that, taken as a whole, specifies a trait. The colloquial usage of the term gene often refers to the scientific concept of an allele.

A Haplotype is a set of allele values for a set of markers across a stretch of DNA.

A Haplogroup is made up of people who have all or most of the same marker alelles in there DNA.

Mutations are a heritable change that occurs in genetic material or a copy error passed on from father to son. They are very useful for tracing one's direct paternal line.

STR or Short Tandem Repeat are markers at some Y-chromosome locations, there are small segments of base pairs that are repeated in the DNA.

SNP or Single Nucleotide Polymorphism is a DNA mutation. SNPs on the Y-chromosome are very rare, but when they do occur, they are passed down unchanged from father to son for literally hundreds of generations. SNPs can, in fact, be used to define entire populations of men.  

Sources: Family Tree DNA, SMGF and Wikipedia webpages.

Case study, the L48+ subclade and the Haplogroups of England

With this information in mind let's analyse the English population. David Boyett sent me some information to test the population of England for the subclade defined by the L48+ marker. I came up with the following figures based on his information:

24,000,000 is the male population of England and 70.9% belong to the Haplogroup Rlb

> R1b = abt 70.9% of [the English population], source Capelli et al.
>
> U106/S21/M405 = 25% of R1b (3,100-3,900 years old) Craig
> Venter and James Watson
>
> L48/S162 = [57]% of U106 (2,900-3,100 years old) [Family Tree DNA]

With these figures I get a current male English population of 2,424,000 or 10.1% that have the L48+ SNP marker. This group is also known as R1b1b2a1a4. As this group is new, little is known of the origin, it could be of Basque/Nordic or Jarstaff origin, but that is just speculation. The rest of the subclade(s) marked by SNP U106+ amounts to 1,829,220 or 7.62%.

With these figures in mind it is possible to work out the Haplogroups of England using the figures from Capelli et al. 'A Y Chromosome Census of the British Isles':

Haplogroup	Percentage of the male English population	Number of present day male English people	Considered Origin
E3b	2.9	696,000	East Africa
I	21.2	5,088,000	Scandinavia
J	3.8	912,000	Southwest Asia
R1a	5.9	1,416,000	Eastern Europe
R1b	70.9	17,016,000	Basque

Note these figures are rough estimate taken from a number of different sources.