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Your genetic sharing with Gunnar (Father)
Sharing 99.8% (low: 0.2%, medium: 97.8%, high: 2.0%)
Your genome was created through the fusion of two germ cells. The sperm cell from your father carried 23 chromosomes and the egg cell from your mother contained 23 corresponding chromosomes. In total, then, your genome is composed of 46 chromosomes, which can be arranged into 23 pairs.
When your parents produced the germ cells that gave rise to you, their chromosomes underwent a mixing process called recombination. In other words, the 23 chromosomes you inherited from your mother were a mixture of the chromosomes she inherited from her parents (your maternal grandparents). In the same way, the chromosomes you inherited from your father are a mixture of the chromosomes he inherited from his parents (your paternal grandparents).
Your chromosomes are therefore a mosaic of your parents’ chromosomes, whose chromosomes were in turn a mosaic of their parents’ chromosomes (your grandparents), whose chromosomes were in turn a mosaic of their parents’ chromosomes (your great-grandparents), and so on, as your genealogy is traced back in time. This means that your genome can be viewed as a mosaic or tapestry made up of fragments of chromosomes from your ancestors. Fragments of chromosomes inherited from very recent ancestors, say grandparents, are expected to be large – typically tens of millions of nucleotides in size. As ancestors become more ancient, then the size of the chromosome fragments inherited from them become smaller – down to a few thousand or hundred nucleotides for ancestors born thousands of years ago.
This tool enables to you compare your genome with another individual in order to determine which chromosome fragments you share and to see how much of your genomes is shared. The fascinating thing about this analysis is that each shared fragment represents a common ancestor. The number of shared fragments and their size reflects the number of common ancestors and how far back in time they are found. In other words, you can see how closely you are related.
When we determine the amount of genetic sharing between individuals, we do not examine all the chromosomes at once. Rather, we break the chromosomes down into fragments of a particular size (the default size is 1 million nucleotides or 1Mb) and evaluate sharing for each fragment.
You can change the size of fragments that are compared, from a minimum of 250 thousand nucleotides (250Kb) to a maximum of 20 million nucleotides (20M). The minimum fragment size will reveal shared chromosome fragments from common ancestors going back thousands of years. The maximum fragment size will reveal only shared chromosome fragments from very recent common ancestors – i.e. going back only a few generations. Fragment size thus represents time depth in the identification of shared chromosome fragments from common ancestors.
As each person carries 23 pairs of chromosomes (i.e. two copies of each chromosome), a comparison between two individuals for any particular chromosome fragment has three possible outcomes:
(1) neither copy matches – defined as “low sharing”, depicted as light blue (2) only one of the two copies matches – defined as “medium sharing”, depicted as brown (3) both copies match – defined as “high sharing”, depicted as orange
The result of your comparison is shown on the image above – for each fragment from each of the 23 chromosome pairs. The greater the number and size of orange and brown segments, the more of your genome you share with the individual being compared. The overall proportion of the genome shared is shown in the image. For a comparison of two distantly related individuals, the proportion of the genome shared is expected to drop as the size of fragments used in the comparison is increased.
Note that the overall proportion of the genome shared is calculated in the same way as in the Genetic Atlas. However, please note that the proportion shown here is derived from a comparison of your genome to only one individual, whereas the Genetic Atlas is based on the average of multiple such comparisons. Also, the proportion reported for the Genetic Atlas is based on a fragment size of 100Kb.