Currently being updated, John Hagan b1940     

Ignore the introduction and go straight to 23andme

There are many introductions to genetics and this one is suitable except it has many adverts - (I ignore those), and they are from Google:

Simple human cell

    Simple human cell



Simple human cell

23 human chromosomes in order of size l to 23.
The X and Y, blue background, are the sex chromosomes.
If the pairs are XX the person will be female and XY for males.
The Y chromosomes passes from father to son virtually unchanged.


The above video plays well with Mozilla Firefox browser.

The image below shows a section of a DNA molecule. Notice the yellow links the green and the red opposite the blue. Pairs are C and G also A and T. Sometimes the sequence is in the +ve (direction) and if the allele is A the -ve (opposite direction) the result is T.

DNA strand
Here cytosine, C has been replaced by thyamine, T. (C>T). This is called a single nucleotide polymorphism or SNP. We may have these mutations C>T, T>C, A>C and C>A. Very rately we have A>C in addition to 7 other similar type mutations, (T>G etc).


The Human Genome Project

This international project that started in 1990 was completed in 2003 cost nearly 3 thousand million dollars. It produced sequences of about 3 billion DNA base pairs ( A-T or C-G) that make up the human genome and found all of the estimated 20,000 to 25,000 human genes. People who are interested in genealogy may have a male relative´s y-chromosome analysed. For example FTDNA, an American company commercially sequences over 300000 base pairs for private individuals. At each specific location there is a specific nucleotide base, for example A (adenine). However someone may find theirs is T allele. This is a mutation. If 2 or more men have this mutation it is recorded as a SNP (pronounced SNIP); if unique to a single person it is called a novel variant.

There are at least 5 different ways to carry out family history research.

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