Tag Archives: inbreeding

Outbreeding Works in a Single Generation

As I have mentioned before, cousin marriages were fairly common among my family. My parents are first cousins. So are my father’s parents. My mother’s parents are second cousins once removed. So instead of 32 great-great-great grandparents, I have only about 18.

Since my wife and I are not related, I wondered how my inbred genome had transmitted to our daughter.

Using David Pike’s ROH utility, I computed the regions of homozygosity for my parents, me, my wife, and my daughter, all tested by 23andme.

I used the default settings for the utility. The total Mb gives the total size in megabases of the long autosomal regions where both alleles are the same. The longest ROH gives the size of the longest such region. Percent Homozygous is the percentage of the genome where the two alleles are the same.

I included the worst chromosome column because of my chromosome 9, which is beyond crazy. This column gives the percent homozygosity of the worst chromosome.

Person Total Mb Longest ROH (Mb) % Homozygous Worst chromosome (%)
Dad 297.45 57.4 72.498% 76.921%
Mom 112.13 22.99 70.662% 79.802%
Me 402.78 71.38 73.588% 93.542%
Wife 37.33 9.64 70.003% 72.411%
Daughter 42.40 8.82 69.936% 71.759%

As you can see, my Dad has higher levels of homozygosity than my Mom as expected and I have the highest levels. My wife is not inbred at all and our daughter has ROH results about the same as my wife. So one generation of marrying someone unrelated, even if from the same/similar ethnicity, has removed all the long runs of homozygosity bred over generations. Good news!

Related Reading

The Kingmaker's Daughter (The Cousins' War)
The Creative Destruction of Medicine: How the Digital Revolution Will Create Better Health Care
Southeast Asia: An Introductory History
In-Breeding: What It Is and What It Does - A Treatise of the Greatest Value to Breeders of All Kinds of Farm and Fancy Stock
Ryan's Occupational Therapy Assistant: Principles, Practice Issues, and Techniques

Genome in the Wild

I tested with 23andme in April 2010 and then upgraded to their version 3 chip with almost a million SNPs last Christmas.

Now I am releasing my personal genome in the public domain.

CC0
To the extent possible under law, Zack Ajmal has waived all copyright and related or neighboring rights to Zack Ajmal 23andme v3 Genome. This work is published from: United States.

You can download my genome data in zipped files:

Razib has a list of people who have made their 23andme genomes public.

When Blaine Bettinger released his genome into the public domain, he issued a challenge:

So, I’m challenging everyone who reads this to download my data and analyze it to find the most interesting or surprising results. For example, you could use my most recent 23andMe V3 data.

I’ve already done a fair amount of analysis myself, including the Promethease reports above (and see here), and a recent blog post about my vastly increased Type 2 Diabetes risk. However, perhaps there’s a recent but relatively study that applies, or perhaps there’s a story you can weave with a handful of SNPs. Or, even better, what can you tell me about my ancestry other than mtDNA and Y-DNA haplogroups? Don’t worry about the strength of the study, reproducibility, etc. – I’m aware of the uncertainties associated with this type of research, and my goal here is to make people aware of possibilities.

Please post your findings in the comments below, and in two weeks I’ll pick the most surprising or interesting findings and make them the focus of a new blog post.

Can you surprise me with my own genome?

I have done a fair amount of analysis on my genome. For example, here’s my Promethease report. My ID is DOD128 in Dodecad, PKEG1 in Eurogenes and HRP0001 in Harappa.

My challenge for you would be to find interesting information about my chromosome 9 which is 93% homozygous.

If you analyze my genome, it would be great if you could let me know about what you found as I am always hungry for more information.

Related Reading

MtDNA: Webster's Timeline History, 1972 - 2007
Public Speaking Bundle: An Effective System to Improve Presentation and Impromptu Speaking Skills in Record Time
The Dramatic Universe: Book 1
Anastasia's Album: The Last Tsar's Youngest Daughter Tells Her Own Story
Script of Harappa & Mohenjodaro & Its Connection With Other Scripts

Inbreeding

I have found out I am actually from West Virginia. Ok, I am just joking.

I knew that my family had a history of marriages among relatives. After all I have only 10 great-great-grandparents instead of the usual 16. With my genome in hand, I set about to quantify the inbreeding.

First, I used David Pike’s Homozygosity tool. It analyzes your genome to find significant runs where the same haplotype is inherited from both parents. Large portions of the human genome are like that. The length of these homozygous regions, however, varies depending on the relation of your parents. If your parents are closely related (first cousins in my case), then you will have longer runs. If your parents are distantly related, then over the generations those genes have had a chance to recombine and so you will have shorter runs that are homozygous.

Overall, the percentage of my autosomal (i.e. on chromosomes 1-22) SNPs that are homozygous is 71.767 and I have 41 runs of homozygosity (ROH) of length at least 200. Here are some of my longest runs:

  • Chr 1 has a ROH of length 6009 (30.95 Mb)
  • Chr 8 has a ROH of length 5819 (33.00 Mb)
  • Chr 9 has a ROH of length 5877 (57.81 Mb)
  • Chr 9 has a ROH of length 5941 (24.38 Mb)

Let’s look at my homozygosity percentage by chromosome.

Chr 1: 71.734 %
Chr 2: 69.952 %
Chr 3: 65.741 %
Chr 4: 71.563 %
Chr 5: 69.270 %
Chr 6: 76.025 %
Chr 7: 69.445 %
Chr 8: 72.690 %
Chr 9: 93.323 %
Chr 10: 69.765 %
Chr 11: 71.866 %
Chr 12: 68.443 %
Chr 13: 74.184 %
Chr 14: 68.571 %
Chr 15: 73.087 %
Chr 16: 66.541 %
Chr 17: 77.555 %
Chr 18: 67.763 %
Chr 19: 66.267 %
Chr 20: 66.228 %
Chr 21: 79.902 %
Chr 22: 69.896 %

A majority of chromosomes seem to have reasonable percentages while chromosomes 4, 6, 8, 11, 13, 15, 17 and 21 are high. However, chromosome 9 is really weird: It is 93.323% homozygous.

David Pike writes that:

So far the largest ROHs in 23andMe V2 data that I am aware of consist of:

  • 9191 consecutive tested SNPs, corresponding to a DNA segment of length 49.99 Mb.
  • 6129 consecutive tested SNPs, corresponding to a DNA segment of length 39.05 Mb.
  • 5594 consecutive tested SNPs, corresponding to a DNA segment of length 28.95 Mb.
  • 4644 consecutive tested SNPs, corresponding to a DNA segment of length 27.71 Mb.

The highest percentage for overall autosomal homozygosity that I have so far seen from 23andMe V2 data is 71.763%.

As you can see, I am an extreme case.

A number of members at DNA Forums reported their homozygous percentage. Of all those listed, mine is the 2nd highest.

According to the paper Genomic Runs of Homozygosity Record Population History and Consanguinity:

South/Central Asians and West Asians have more than three times as many ROH in all categories over 4 Mb long than sub-Saharan Africans and other Eurasians. 19% of individuals from these populations have ROH over 16 Mb in length, consistent with the high prevalence of consanguineous marriage (marriage between individuals who are second cousins or closer) in these populations.

My total ROH length (segments > 0.5Mb) is about 282Mb which is about 1.2 standard deviations above the Central/South Asian sample mean in that paper. But I am more than 1.7 standard deviations above the mean for longer segments (>5Mb).

Let’s take a look at a graph from the paper’s supplemental material which plots total ROH length versus number of homozygous segments:

My inbreeding coefficient based on the length of long (>5Mb) runs of homozygosity in my genome (fROH5) is about 0.11 while the average in the Central and South Asian sample for the HGDP dataset is 0.015 (not directly comparable due to different number of SNPs used to calculate).

Finally, I used Plink to calculate my inbreeding coefficient F using all the South Asians from my reference datasets. That coefficient comes out to be 0.1184.

Related Reading

The Official Guide to Ancestry.com
South Asia in the World: An Introduction (Foundations in Global Studies: the Regional Landscape)
Lonely Planet Southeast Asia (Shoestring)
Deep Ancestry: Inside The Genographic Project
DNA & Genealogy