Michael Tobias is our speaker. During the Covid19 pandemic in the UK I was approached by several people whose recent DNA tests had revealed Jewish ancestry (typically an unknown Jewish birth father). This talk will give a brief overview of DNA testing and will cover one such case. I will provide an overview of the steps taken in under 2 weeks to construct a family tree of over 800 individuals including over 40 DNA matches and identifying the Jewish birth father. In the process the accuracy of the DNA-estimated family relationships could be compared with the true family relationships and the impact of any endogamy could be analysed.