This is a guest report from a geneticist

 

For more than two decades, the McGregor DNA project has been building a remarkable picture of shared heritage for Clan Gregor. We see that DNA is passed down through families in predictable but sometimes surprising ways, shaping how we are connected to one another. By understanding how this process works, we can better appreciate what our results are telling us and how they fit into the wider story of our family histories.

This post revisits the biological basis of genetic inheritance and explores it in the context of our DNA project. One thing quickly becomes apparent - understanding genetics is almost like learning a new language. There are many specialised terms and interpreting them is often the first step towards making sense of the bigger picture. Most of these terms will be written in italics when first introduced in this post.

Genetic inheritance

 All genetic inheritance begins with a biological process called meiosis, a specialised form of cell division that halves the number of parental chromosomes, producing sperm or egg cells a.k.a. gametes that carry a unique mixture of maternal and paternal DNA. This short video from the BBC explains the process. Human sperm cells carry 22 autosomes (chromosomes 1-22) and one of the sex chromosomes, either X or Y. Each chromosome on average carries approximately 2 metres of DNA made up of nucleotide bases which code for everything that makes us human.

 

Human eggs carry 22 autosomes and an X chromosome. Interestingly, eggs are the larger gamete containing mitochondria and other molecules to guide the developing embryo. Mitochondria contain their own DNA (mtDNA), which is inherited by both males and females from their mother, but only females pass it on to the next generation.

At fertilisation, male and female gametes combine to form a zygote and through multiple cell divisions during embryonic development, a new individual develops made up of trillions of cells, each containing 46 chromosomes. Males have 44 autosomes and XY sex chromosomes while females have 44 autosomes and XX.  All males inherit their Y chromosome paternally and their X maternally. Females inherit one X from each parent.

We don’t inherit an exact copy of our parents’ chromosomes

Along with halving of parental chromosomes, meiosis also involves recombination of chromosomes where DNA from the two copies of each chromosome is shuffled before being passed on. As a result, we don’t inherit an exact copy of our parents’ chromosomes, and they didn’t inherit an exact copy of their parents’ and so on. In just a few generations our DNA can be very different from our ancestors. Because of this, autosomal DNA (chromosomes 1-22) is limited to detecting relationships to approximately six generations, although linking these matches to specific surnames can be difficult without supporting genealogical information.

The X chromosome follows a different inheritance pattern, so X matches can provide additional clues about possible lines of descent, although they do not usually point to a single ancestral line.

The Y chromosome and paternal inheritance

The Y chromosome behaves differently during meiosis.

The majority of the Y chromosome does not recombine. Instead, it is passed from father to son largely intact, forming a continuous line of inheritance over many generations. This unusual stability is what makes Y‑DNA so powerful for tracing paternal ancestry. It also means that any changes that do occur are preserved and can be followed through time.

Mutation: a source of genetic variation

Mutations arise as part of the normal process of DNA replication, although their frequency can be influenced by factors such as age and environmental exposure. Mutations are often thought of as ‘bad’, but in most cases they are biologically neutral with no effect. Only mutations in gamete cells are passed on.

 

Despite its relative stability, the Y chromosome undergoes mutation events. These mutations are the source of variation along a paternal line. A DNA test does not measure ancestry directly, but the outcome of these mutational processes.

Two main types of mutation are relevant in Y‑DNA analysis:

1. single base changes in the DNA sequence, called single nucleotide polymorphisms (SNPs)
2. changes in the number of repeated DNA sequences at specific locations, called short tandem repeats (STRs)

These mutations occur at very different rates.

Haplogroups vs Haplotypes

SNPs arise relatively rarely. When they do occur, they tend to be inherited by all descendants of the individual in whom they first appeared. A haplogroup is a branch of the Y chromosome tree defined by shared SNP mutations. In practice, haplogroups are often experienced as large, overarching branches representing lineages that extend far back in time, although modern sequencing can now identify increasingly specific sub-branches within them, sometimes within genealogical timeframes. Haplogroups help answer the question, “Which major branch of the lineage does my paternal line belong to?”

If a haplogroup describes where a lineage sits on the tree, a haplotype describes how that lineage varies within its branches.

With STRs, which mutate more frequently, the number of repeats can increase or decrease from one generation to the next. This produces small, incremental differences between related individuals. A haplotype is a set of linked genetic markers that are inherited together. In Y‑DNA testing, this typically refers to a set of STR marker values (such as DYS393, DYS390, etc.) that together describe the genetic profile of a paternal lineage.

This is how many surname projects were built, by recognising patterns of similarity across STR profiles.

A model, not a record

One important point follows from this.

DNA testing does not reconstruct the past directly. Instead, it models how mutations accumulate over generations and interprets present-day variation in that context. These models are based on observed mutation rates, derived from large numbers of known relationships, such as father/son pairs and documented family lineages. By incorporating these rates, they estimate how likely it is that a given pattern of differences arose over a particular number of generations.

Matches, distances, and predicted relationships are therefore not exact measurements of ancestry, but statistically informed interpretations of biological processes. This does not make them unreliable, but it does place them into context.

From separate systems to integration

 Historically, STRs and SNPs were often treated as separate tools. STRs were used to compare individuals and detect relationships while SNPs were used to assign broad haplogroups. This led to a simplified view that STRs were linked to “recent ancestry” while SNPs were linked to “deep ancestry”. However, this distinction no longer holds in its original form.

 

Advances in technology: the shift to Y700

 Modern sequencing approaches, such as Big Y‑700, have transformed how Y‑DNA is analysed. Rather than testing a fixed set of markers, Y700 sequences large portions of the Y chromosome. both STR variation and thousands of SNPs, identifying both known and previously undiscovered mutations.

 

New SNPs discovered through testing can define previously unknown branches, so that the structure of the tree is continually being improved. In this sense, modern testing does not simply use the tree, it contributes to building it.

 

Ongoing surname projects, such as the MacGregor DNA project, illustrate how these principles play out in practice. Initial groupings are often based on similarities in STR markers, suggesting possible shared ancestry. However, as more detailed SNP data become available, particularly through tests such as Y700, some of these apparent relationships are confirmed, while others are shown to be misleading. This reflects the underlying biology - patterns of variation can suggest connections, but only the structure defined by shared mutations can fully resolve them.

 

Types of DNA testing: strengths and limitations

 

Different types of DNA tests provide different kinds of information, and each has strengths and limitations.

Autosomal DNA
Identifies relatives across all ancestral lines but within recent generations only and often cannot specify which ancestral line a match comes from without supporting records.

Y-DNA testing
Traces the direct paternal line and is particularly useful for surname studies but only follows paternal ancestry.

mtDNA testing
Traces the direct maternal line, but like Y-DNA represents only one ancestral pathway.

 

For this reason, DNA results are most powerful when combined with genealogical research rather than interpreted in isolation.

 

Final thoughts

DNA testing provides powerful insights into shared ancestry, but those insights sit within a biological system shaped by mutation and a statistical framework used to interpret it. By recognising how haplogroups define the broader structure of lineages, and how haplotypes capture variation within them, we can read our results with greater clarity. For a project that has been building evidence over more than 20 years, this perspective allows us to move beyond simply observing patterns to understanding what those patterns mean, and where their limits lie.

 

 MacGregor DNA project blog update 2026 

If DNA genealogy has taught us anything it is that surnames have many origins, and the adoption of a surname does not indicate a direct relationship with another individual simply on the basis of that surname.  In this version of the blog, I am going to concentrate on one group only to show it is possible to look for similarities but that what STRs show us can sometimes be misleading because of the fact that mutations are random. In other words, it is possible for two individuals to have the same mutations but not share a common ancestor and this has proved that SNP testing is vital in order to find and verify connections which are suggested by the STRs. But, we have to be prepared for these apparent connections to be disproved, or thrown into doubt, by the more detailed results that SNPs give. Also the time frame within which shared SNP results operates can vary from 200 to perhaps 1600 years.

 

I am going to concentrate on the MACGREGOR distant group – partly because with so many people in it one would expect that there will be some shared origins and, because of dating predictions given by the SNP analysis, we can attempt to date when two people shared the common ancestor.

 

Before I begin, I just want to reassert some facts about the nature of clanship – that is the idea of belonging to a clan. There is a misconception that all members of a clan descend from a single individual – and more precisely an individual of the name. On the contrary, the thinking behind clanship is that people with similar names are united as a single clan - so individuals named Gregor and Gregory for example, despite having multiple genetic origins are all considered part of Clan Gregor. There is also an idea current that all people in a clan MUST descend from a common ancestor, which in Clan Gregor's case would be the Argyllshire branch. This is not the case. For example, the Perthshire Gregors/Grigors who became McGregors are genetically different in origin from, and therefore not related to, the Argyllshire MacGregors. They are members of Clan Gregor as much as the Argyllshire MacGregors are. If name origins are correct the name Gregor might well  mean something like 'watcher', or ‘watchful, vigilant’ and is believed to come from the Greek ‘gregorein’ 'to be watchful’.  

 

A M(a)cGregor who has Viking genetics is still clearly a member of the clan – and this genetic origin could have come about through adoption, illegitimacy or the fact that the surname was simply assumed at some point in the past. In Highland society the 'Common Man’ for want of a better way of putting it, might well have been living on the land as a tenant of some landed individual, and was only called by what is known as patronymics – so John whose father was Donald whose grandfather was Peter would be known as John MacDonald VicPatrick  or in Gaelic Iain mac Dhòmhnaill mhic Pheadair. No need for a surname. However, as populations expanded and individuals became more settled on the land, it was important to the landowners to be able to rely on tenant’s support – in the best case this was a symbiotic relationship – but not always. One way to ensure loyalty was for individuals to adopt the landowner’s surname.

 

The MACGREGOR distant group includes individuals from a wide variety of backgrounds.  This statement could be applied to any surname group in the DNA project.  Because of the limitations that STRs have, I have had to omit any results which had 25 or less STRs tested. There are therefore 101 others who remain, of whom 38 have done either Y500 or Y700 and surprisingly out of those only four pairs of individuals match each other closely as far as is indicated by terminal SNPs.  Of the 101 people with 37 markers or above 77 have 67 markers and 59 have 111 markers.  Using Dean McGee’s Y Comparison Utility and Splitstree I have created two spider charts, one with the 37 results, and one with the 111.  I have underlined some of the same  kit numbers in the 37 as are in the 111, and you will see that some results look to be closer in 37 then they actually are when you look at 111.  In 37, kit 1006596 seems to be the origin point of a number of different branches, whereas in 111 it is just another branch with a possible common origin (on both charts it is on the left).

 

These charts are based on probability of 75%, with the FTDNA mutation rate 0.004 etc, and 30 years per generation.

                                   MacGregor Distant 37 markers                                                               

                                   MacGregor Distant 111 markers                                                                    

Using Dean’s comparison grid the group in the bottom left-hand corner containing 98616 to 126138 show as being possibly related to each other (that is, have a common ancestor) between 120 and 210 years  ago. The only other group which suggests even a degree of recent relationship is the one containing 941169 and M135332 but the estimated time distances vary between 600 and 1710 years [this is the group at the very top of the chart].  Occasional pairs show some relationship: so, 448450 and IN22242 are suggested to have a common ancestor 450 years before, IN132077 and B908902 within 390 years, I99742 and 395944 the same, and 430122 and 245917 of 300 years. A closer link of 120 years is suggested for 404828 and 170627, between 60 and 120 years for 941518, 153532 and 164088, and finally 270 years between 981710 and IN124384.

 

All other shared ancestors are suggested to be between 1440 and 5850 years ago.

 

What we will do now is look at these possible relationships in detail to see if the SNP results confirm or contradict what is suggested by STRs.

 

The above groups and pairs will now be dealt with in sequence.

 

1)     185487, 173181, 126138, 667833, 200914, and 981616

In this group unfortunately only one person has undertaken Y700 and shows an ancestral split around 1400CE . One other participant suggests that this group may all connect to William McGregor the early 18^th century preacher in America. I would expect that all the others would be related to that person – either ancestral or descendant from, but we would need at least another Y700 result to confirm this.

 

2)    94589, IN109971,135116, 28296, 941169, 395944, 43065, MI35332

This group shows a variety of M(a)cGregor ancestors, not obviously related, and one McGown. Five of these have done Y700 and the terminal SNPs are BY69722, FT213382, FT47815, FT371661 and S7361.  Almost all of these are connected with at least one other result at  between 400 and 450CE  or 1600 years ago according to the FTDNA dating. 

 

Kit number 94589 McGregor actually shares a common ancestor at c550CE, by FTDNA reckonings, with 38516 McLaren – again this connection would have happened pre surnames. The same applies to 135116 Peddie with 28296 McComas McGregor who both have later SNP splits, but who share a common ancestor at S744 around about 400CE to 450CE.

 

3)    448450 and IN122242

Both these individuals share SNP FTF57555. This mutation arose around 1500CE but since both have ancestors called (christian name)  Angus with slightly different dates of birth (and apparently a close geographical connection) it is clearly probable that they are related to the same ancestor one or two generations back from what they currently have found genealogically. The 111 mutation chart shows these two lines as joining to form one.

 

4)    IN132077 and B908902 (and 138485 not shown on the chart)

 

IN132077 and 138485 share a common ancestor (or, rather, share a mutation FTF403 borne by a common ancestor) at c1450CE while B908902 descends from that original by a mutation which happened about 1600CE (SNP FTE86294).  One of these McGregors comes from a group associated with Gregor/McGregor families round Perth (138485) so it would be a good idea for IN132077 and B908902 to investigate this area for a genetic connection. I have now moved both these results from the McGregor distant section to the (Mc)Gregor  group which heads the results grid.

 

5)    IN99742 and 395944

Kit 395944 actually shares an origin at 550CE with IN99742. The Splitstree programme puts these results in separate areas  which suggests that both individuals, although having the McGregor name are accidentally related through surname choice only (since their shared SNP is c550CE). However, it would be worth doing more genealogical searching since looking at their earliest ancestors, these could be in fact be brothers or direct cousins and they clearly would share the same ancestral SNP no matter how distant. The only key difference in their STR results is the fact that DY385 (one of the early DNA results) has a significant and unusual one step difference, but that has been enough to put the two results into separate lines. If the two individuals involved would make contact, we can try to find if the connection is much closer than suggested by DNA.

 

6)    430122 and 245917

Neither of these individuals has done a Y700 test so it is not possible to compare them – in addition 245917 has not detailed earliest known ancestor. The 111 chart suggests that they are connected genetically at some point in the more recent past. More DNA information and genealogical information is needed.

 

7)    404828 and 170627

As shown by their earliest known ancestor entries these two individuals have a common ancestor born in 1802. Not surprisingly they have SNP FT87169

 

8)    941518, 153532 and 164088

These three are all descended from the same individual – a William McGregor who died in 1815 in North Carolina. They have SNP FTF1629 – this SNP was estimated to have split from MF409 around 1800 which suggests that it was actually William himself who acquired the mutation from his father whose mutation MP409 arose around 1600CE

 

9)    981710 and IN124384

These two individuals are probably quite closely related but one (981710) has not tested to Y700.  The common ancestor dates back to 950CE but from that ancestor the SNPs go back in time to M222 (arose c50BCE) which probably has its origins in Ireland.

 

It seems that, for the most part, when the the 111 SNP grid is used for comparisons it produces the correct connections between kits, but not100% of the time.

 

The process I have used here could be used with any of the surname groups with diverse entries so long as sufficient numbers of individuals have done 111 markers and preferably Y700. As usual, if anyone would like me to run a similar exercise with entries from a name group then please provide 10-12 entries you want to compare with. Please remember that it needs ideally  to be individuals who have done the Y700 test.

 

Contact me at richardmcgregor1ATyahoo.co.uk, substituting @ for AT.

 

With thanks as always to the authors of Splitstree, and Dean McGee.