MapS Phasing | Introduction

Hello everyone, and thank you for your interest in MapS Phasing. Today I would like to introduce MapS Phasing to you – a tool for genetic genealogists which will phase your DNA data. In the first video, I will explain what phasing is, and why you would want to phase your DNA data. When we receive our DNA results from the testing company of our choice, we start by exploring our matches on the companies’ own sites. When we start to work more extensively with our results, we will download the raw data files and maybe upload them to a site like If you ever take a look into these raw data files, you will see a long list of tested SNPs. Depending on the file format, you will see some identifier, usually the rsID, the chromosome number, the position on that chromosome and the genotype at that position. The genotype is represented by a combination of two letters, each either A, C, G or T. There are two letters, because we inherit one allele from our father and one from our mother. However, in the raw data files of the testing companies, the paternal and maternal alleles are not sorted or separated. A letter on either position could come from either parent. The process of assigning the alleles to the paternal and maternal chromosome is what we call phasing. Having such phased data is useful for several reasons: firstly, it can eliminate false positives matches and secondly the phased data can be a substitute for a parent that has not been tested. Particularly, if you combine the phased data of multiple children, the result will resemble the test result of the non-tested parent, which can be useful, for example, to better estimate the distance with other DNA matches to the most recent common ancestor. MapS Phasing does all of this automatically for you. All you have to do is enter the information of the family group into a small family tree, click a button and MapS Phasing will phase the children’s DNA data, and create a data file for the parent that has not been not tested. In the next videos, I will show you in detail how to register for and install MapS phasing, how to start a simple phasing project, how to improve your phasing results by adding data of another relative and finally I will explain the output files for you. This was the introduction to MapS Phasing. My name is Hendrik Wendland and if you have any questions, concerns or suggestions, please feel free to email me at [email protected] Again, thank you for your interest in MapS Phasing and I wish you all the best for your genealogical endeavors.

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