The Puny Y Chromosome

The Backbone Element of the Ewing Brick Wall Project

DNA Background

We humans have 46 chromosomes (23 pair) found in just about every cell in our body. We received half (23) from each of our parents who mixed and matched their 46 chromosomes (half from each of your grandparents) during meiosis the parents 46 are reduced to just 23. The DNA within each chromosome are pairs (base pairs) of nucleotide acids called adenine, guanine, cytosine, and thymine but we just refer to them by their initials: a, g, c and t. There are about 3 billion base pairs of DNA in a humans genome (complete set of DNA). DNA.

A male only mixes and matches the non-sex autosomal chromosomes --pairs 1-22. His 23^rd pair are an X he received from his mother and a Y he received from his father. The X and Y do not mix and match.

Each of the nearly 100 million sperm created during meiosis contains 23 NON-paired chromosomes, 1-22 are a mixed and matched-combined version of his parents. The 23^rd in about 50% of the sperm is an exact copy of the X that he received from his mother and the other 50% of the sperm has an exact copy of the Y he received from his father.

All of a female’s chromosomes can be mixed and matched (recombined) and the egg she creates has 23 NON-paired chromosomes and the 23^rd is always an X that is usually a mixture of her father's and her two maternal grandfathers, but sometimes she just gives a copy of her fathers!! Click this website for a more detail review.

We call this mixing and matching “recombination”, and it is what leads to “genetic variation” that makes each of us unique.

The Y Chromosome

As discussed above, the Y chromosome never recombines with another Y chromosome, because males have one X and one Y and females have two XX’s, so there isn’t a chance to match with any other Y.

That means that the Y is passed from father to son, generation after generation with no recombination change. A males Y chromosome looks essentially just like his GGGGGGGFather’s GGGGGGFather’s.

The Y has about 59 million of the 3 billion base pairs and it is the smallest of all the chromosomes and has been called “the puny” one. Even though there is no recombination of the Y it does change by mutating. About every couple generations one or two of the 59 million base pairs has a hiccup and mutates; namely one of the acids is switched to a complementary – example: adenine (a) is replaced with a guanine (g) or thymine (t) is replaced with ccytosine (c) without any detrimental coding effect because these mutations generally happen in the none coding regions (genes) of the Y chromosome. The Y only has a few genes. A gene is an region of a chromosome that provides genetic coding which determines our traits, i.e., 2 feet, blue eyes, no ear lobes, etc. The genes that the Y does have mostly deal with creating more males. BTW, only about 1% of the human genome is made up of coding genes, so most mutations which are called SNPs (pronounced snip and means single nucleotide polymorphisms) have no impact on our biology. Single nucleotide polymorphism is a big term which means that one of the base pair (single) of acids (nucleotide) changed—and now that location has two or more different forms (polymorphism).

STR and SNP Testing

In certain regions of the Y chromosomes tandem mutations tend to repeat over short segments in a head-to-tail manner and are called Short Tandem Repeats (STRs). They are relatively easy to test for and therefore cost less than SNP testing. Y STR testing has been the workhorse of Y DNA testing for years, however, because testing technology and Y SNP mapping has progressed rapidly over the past few years most Y Surname project administrators are currently recommending full Y SNP testing such as the Big Y at Family Tree DNA instead of the STR test panels.

The analogy a compass and GPS is a pretty good way to consider the two types of tests:

STR tests were given for 12,25,37,67 and 111 different marker regions, with 37 being the most popular. STRs can give a solid accurate “direction” of lineage and can be considered like a compass.

The Big Y SNP testing will find about 70,000 SNPs and is more like a GPS that can provide a “pinpoint” lineage . And the cost difference of the two types of test is also like a compass and GPS. Compasses are typically much cheaper than equivalent level of a GPS. The cost at the end of 2022 was $119 for the Y37 STR Panel and $449 for the Big Y. The Big Y cost ,if you previously had STR testing, can be as low as $239

The backbone element of the Ewing Brick Wall project is the Ewing Y DNA Project especially as the number of members obtaining the Big Y results continues to grow. Please review the Project overview and consider joining the Ewing Y DNA Project if you have the Ewing surname