What would be the result if all human life was destroyed except for 7 humans? I am referring to noah and his family. What would the genetics look like after 6000 years?
I will address mtDNA (mitochondrial DNA) as that is the only one with which I have direct experience.
You would have a severe bottleneck, with diversification from that point on expanding to fill all other areas of the world.
All mtDNA genomes from prior to a worldwide flood, commonly attributed to ca. 4,350 years ago, would be terminated -- with the sole exception of the genomes of Noah's female kin and companions.
In most areas of the world you would find skeletal populations with pre-flood mtDNA up to a certain time -- the flood -- but those would be abruptly terminated and subsequently replaced by mtDNA attributed to the Middle or Near East. Those would be Noah's female kin and companions. If there was a worldwide flood with 7 survivors the break would be very distinctive and absolute.
Instead what we find are mtDNA patterns whereby the ancient genomes persist in many cases right up through modern times.
One example: a skeleton dated >9,000 years old from southern Alaska was found to have a rare haplotype which was found in modern populations stretching from California to the tip of South America. This shows both continuity of the mtDNA haplotype and the lack of a break ca. 4,350 years ago. It also shows evidence of an early coastal migration.
A second example: from my own archaeological research I have a skeleton dated 5,300 years ago that had the same mtDNA haplogroup as modern descendants in the same area.
In both cases we have no drastic break ca. 4,350 years ago, but rather a persistence of mtDNA types from before to after the date attributed to the global flood.
These two examples are but a drop in the bucket -- there is similar, and better, evidence showing the same thing from most parts of the world.
And the evidence is not limited to genetics. We see continuity throughout the world in linguistics, human cultures, fauna and flora, as well as many other aspects of the natural world. Tree rings, glacial varves, and coral growths show no break ca. 4,350 years ago. Nor do the fields of geology or sedimentology.
While rambling, I hope this answers the question you asked.
Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.