Y Chromosome DNA Test

Overview

A Y chromosome DNA test (Y-DNA test) is a genealogical DNA test used to investigate a man's patrilineal (his father's line) ancestry. The Y chromosome, like the patrilineal surname, is nearly identical from father to son. Occasionally, errors in the copying process occur, and these mutations can be used to determine the time range in which two people share a most recent common ancestor, or MRCA. They are connected within a genealogical time range if their test results are a perfect or nearly perfect match.

Each individual may then look at the other's father-line information, which normally includes the names of each patrilineal ancestor and his spouse, as well as the dates and locations of their marriage and the births and deaths of both spouses. The two people who have been matched may discover a common ancestor or MRCA, as well as any information the other possesses about their shared patriline or father's line prior to the MRCA. Y-DNA testing are usually coordinated as part of a surname DNA study. And if the other agrees, each obtains the other's contact information.

Women who want to know their direct paternal DNA ancestry can request a test from their father, brother, paternal uncle, paternal grandpa, or a cousin who bears the same surname lineage (the same Y-DNA).

What is Y Chromosome?

In humans, the Y chromosome is one of two sex chromosomes (the other is the X chromosome). Each cell contains one of the 23 pairs of human chromosomes, the sex chromosomes. The Y chromosome covers more than 59 million base pairs of DNA and accounts for almost 2% of total DNA in cells.

Each cell in a human generally has one pair of sex chromosomes. Males, who have one X and one Y chromosome, have the Y chromosome, whereas females have two X chromosomes.

Identifying genes on each chromosome is a hot topic in genetics. The estimated number of genes varies because researchers utilize different methodologies to determine the number of genes on each chromosome. The Y chromosome most likely includes 70 to 200 genes that code for proteins. Because the Y chromosome is found solely in males, the genes on this chromosome are thought to be important in male sex determination and development. The SRY gene, which is responsible for the development of a baby into a man, determines sex. Other genes on the Y chromosome are required for males to father biological offspring (male fertility).

Many genes are exclusive to the Y chromosome, while genes in pseudoautosomal regions can be found on both sexes. Men and women each have two functioning copies of these genes as a result. Many of the genes found in pseudoautosomal areas are required for proper development.

Health Conditions Related to Y Chromosomal Changes

The following chromosomal conditions are associated with changes in the structure or number of copies of y chromosome.

    1. 46,XX testicular difference of sex development.

Most cases of 46,XX testicular sex development are caused by an improper exchange of genetic material between chromosomes (translocation). This exchange happens at random during the production of sperm cells in the afflicted person's father. The SRY gene, which is ordinarily present on the Y chromosome, is misplaced, nearly exclusively onto the X chromosome, in the translocation that causes 46,XX testicular difference of sex development. An individual with an X chromosome who contains the SRY gene may develop as a man despite not having a Y chromosome, but will be unable to generate sperm to father biological offspring.

    2. 47,XYY syndrome.

47,XYY syndrome is characterized by one X chromosome and two Y chromosomes in each cell, for a total of 47 chromosomes. An extra copy of the genes found in the pseudoautosomal region of the Y chromosome may explain the long height and other characteristics seen in people with this disorder.

Only part of the cells in persons with 47,XYY syndrome have an additional Y chromosome. This is known as 46,XY/47,XYY mosaicism.

    3. 48,XXYY syndrome.

The presence of an extra X and an extra Y chromosome in cells causes 48,XXYY syndrome, a disease that leads to infertility, developmental and behavioral difficulties, and other health concerns. Although afflicted individuals are frequently assigned male gender at birth, extra genetic material from the X chromosome interferes with sex development. Small testes that do not operate correctly cause testosterone levels to drop (a hormone that directs male sex development). Extra copies of genes from the extra X and Y chromosomes' pseudoautosomal regions are believed to contribute to the signs and symptoms of 48,XXYY syndrome.

    4. Y chromosome infertility.

Small deletions of genetic material in certain sections of the Y chromosome result in Y chromosomal sterility. This disorder impairs sperm production, making it difficult or impossible for affected individuals to father children. The deletions occur in Y chromosomal regions known as azoospermia factor (AZF) regions. Genes in these areas code for proteins that are suspected to be important in sperm cell formation, while their precise activities are unclear.

Deletions in the AZF areas result in the deletion of all or a portion of many genes, or, in rare circumstances, a single gene. The absence of this genetic material is likely to limit the creation of one or more proteins required for proper sperm cell growth. As a result, sperm develops incorrectly or not at all, resulting in Y chromosomal sterility.

    5. Other chromosomal conditions.

Other chromosomal disorders involving the sex chromosomes can also have an impact on sex development and fertility. These conditions' signs and symptoms vary greatly and range from moderate to severe. They can be caused by sex chromosomes that are missing or have additional copies, or by structural alterations in these chromosomes.

In rare cases, more than one additional copy of the Y chromosome might be found in each cell (polysomy Y). The existence of two additional Y chromosomes, for example, is represented as 48,XYYY. The excess genetic material in these circumstances can cause skeletal deformities, lower IQ, and delayed development, but the characteristics of these disorders vary.

Why Should You Care About Y Chromosome DNA Test?

Family historians can benefit greatly from Y-DNA testing.

Because a man's Y-DNA chromosome is essentially similar to that of his father, grandpa, great-grandfather, and so on, a Y-DNA line may be traced back hundreds, if not thousands, of years.

Because many cultures follow the patrilineal line, there is typically a strong link between the family name and the Y chromosome.

As a result, Y-DNA testing is extremely useful for male adoptees seeking information about their biological father surname and paternal family members. One caveat is that, like atDNA testing, Y-DNA testing may disclose misattributed parentage—the test-findings taker's may imply an entirely other family name link or provide unexpected genetic matches.

Before making any conclusions, thorough investigation should always be performed. The benefit of having the same Y chromosome passed down through the ages is also useful for determining whether a paternal line has a certain ethnic or geographic origin. 

For example, if your patrilineal line had African or Native American ancestors, the identifying Y-DNA pieces will remain the same for dozens of generations. Furthermore, Y-DNA testing is beneficial for narrowing down genetic matches on a single paternal line. While autosomal (atDNA) cousin matches can share on any of the other 22 pairs of chromosomes, Y-DNA cousin matches can only share on the Y chromosome.

Completing a Y-DNA test is also advantageous when you have hundreds of atDNA matches but are having problems establishing who belongs on your paternal line of interest- Y-DNA test results will likewise offer many matches, but they will all belong to the same Y ancestral line. Conversely, a problem with having an unchanging Y chromosome is that it cannot clearly determine a common ancestor relationship within recent generations.

All direct male descendants of a paternal line share the same Y-DNA, regardless of how long ago they lived.  

Y-DNA testing can only detect whether two ancestors had a male family relationship—father and son, siblings, male cousins, uncle/nephew—or estimate the number of generations since two men shared a common paternal ancestor.

This is why it is critical to do both Y-DNA and atDNA testing to acquire the most insight into your findings.

Combining your atDNA findings with your Y-DNA results will help you determine how far back a shared ancestor is on the Y-DNA line, because atDNA identifies genetic matches that typically occur within a 1-8 generation span.

Choosing the Right Test Taker

Women cannot take a Y-DNA test since the Y chromosome is inherited only by men, but women may use Y-DNA testing to help break down paternal-line brick walls! To choose a potential Y-DNA test taker, you must first understand how the Y chromosome is passed down via your family tree.

If a line "daughtered out," that is, if a father had only daughters and no boys, the Y chromosome inheritance terminated with that father.

The most straightforward technique is to create or print a family tree for your target ancestor and highlight any males derived from that ancestor who would have inherited that man's Y chromosome. You may need to contact a distant cousin to discover a qualified test-taker.

• Y-DNA Testing:

There are two forms of Y-DNA testing: Short Tandem Repeat (STR) and Single Nucleotide Polymorphism (SNP).

The findings are compared to other test-takers in the testing company's database to discover genetic similarities, just like the more widespread atDNA test.

• Y-DNA STR Testing:

The most popular way to begin Y-DNA research is via STR testing. STR markers are short segments of DNA that run along the Y chromosome, and the test searches for sequences of DNA units that repeat a varied number of times.

These distinct sequences are handed down through generations and can aid in determining the genetic link between two test-takers.

Testing 67 or 111 markers is advised since more markers checked can yield better findings.

• Y-DNA SNP Testing:

SNPs are differences in a single unit of DNA rather than a region, hence this form of test delves considerably deeper into the specifics of Y-DNA.

Most people will begin with a Y-DNA STR test and may then move on to a Y-DNA SNP test to better characterize a test-results taker's and discover their ancestral haplogroup—their branch of the human genetic tree.

How to Take a Y DNA Chromosome Test?

Follow the instructions given with the kit to take a Y DNA test. Many tests may be done at home. The overall method is as follows:

1. Purchase the test kit online: You may place your order immediately on the company's website. You may also purchase from third-party websites like Amazon. The test kit will be delivered to the address you supplied.
2. Open the kit and register: Before using a Y DNA testing kit, several firms need you to register it on their website. During the registration process, you may be required to provide certain personal information to assist their study.
3. Collect the sample: Collect the sample in the manner specified on the kit. Some kits may ask you to provide a saliva sample, while others may require you to scrape your inner cheek walls with a swab. The information on the label will tell you which one is necessary.
4. Mail it back to the company: Label the sample and send it directly to the company where it’ll be analyzed.
5. Wait for your result: You may have to wait 4-6 weeks for a Short Tandem Repeat (STR) test or longer for a more comprehensive Big Y-700 test. Most companies will send you an email when your result is ready. You can then login into their website and download your result.

Who Can Take a Y Chromosome DNA Test?

Because the Y chromosome is exclusively inherited through the paternal line, the Y DNA test is only for men. For example, because your mother cannot pass Y DNA, you would be unable to find your maternal grandpa using Y DNA testing. If you are a man and wish to trace your ancestors back to your grandpa, a Y chromosome test might be a good option.

To summarize, only a man may do this test to analyze his father, grandpa, great-grandfather, and so on.

Understanding Test Results

The names of the markers examined, as well as their associated values, will be displayed in the Y-DNA STR test results.

The majority of marker names begin with "DYS" (D for DNA, Y for the Y chromosome, S for the segment) and the marker number, such as DYS438.

The value assigned to a marker represents the number of sequence repetitions discovered at that place. So, if DYS438 is 7, it signifies that 7 sequence repetitions were discovered at that site.

Comparing the values of the same markers in two or more men can reveal if they are genetically related; the more values that match, the more likely those guys are connected.

And, the more markers you test, the more accuracy you will gain in determining if test-takers are related to each other.

A difference of 2 on a 37-marker test, for example, may suggest a lower likelihood of a genetic match, but a difference of 2 on a 111-marker test indicates a significantly higher likelihood of a genetic match.

The difference threshold increases as the number of indicators tested increases, as does the pool of probable genetic relatives.

Y-DNA test results also include haplogroups, which may be used to establish which branch of the human ancestral DNA tree a test-Y taker's chromosome comes from.

Y-DNA STR testing offers an estimate of a haplogroup, but Y-DNA SNP testing provides a conclusive haplogroup diagnosis.

A Y-DNA haplogroup starts with a main branch and then continues into narrower and narrower subgroups, which are defined by one or more SNP mutations.

Each unique mutation will also determine the ancestral and ethnic origins of the haplogroup.

The resources provided below will give you a great in-depth look at Y-DNA testing and haplogroup research.

Conclusion

The Y DNA test, also known as the Y chromosome DNA test, is a male-specific genealogical DNA test that is used to investigate a man's patrilineal or direct father's-line heritage. To grasp the test idea, you must first comprehend the Y chromosome.

The Y chromosome distinguishes males and females genetically. It is also known as the "sex chromosome" since it determines whether a kid is biologically male or female.

Males inherit one X chromosome from their mother (who has two) and one Y chromosome from their father (who has one X and one Y chromosome). Except in the case of a mutation, the Y chromosome does not change. If there is no change, the same Y chromosome that your great grandpa had from his father will be handed down to your grandfather and father, and eventually to you.

Because the Y chromosome transmission chain from father to son is mostly unchanged, the Y DNA test will assist males in tracing their ancestors through their paternal line and learning more about their family history. Although not as conclusive as a paternity test, a Y DNA test may be used to locate a father. It may even travel farther back in time to look for your great grandpa or great-great-grandfather, and so on.

Because the Y chromosome is exclusively tested for in men, the Y DNA test provides no information regarding the maternal lineage.