I watch the TV show The Last Man on Earth and there is only a handful of women and men living. In the show the few are trying to conceive. They haven't covered how eventually they will have to inbreed a generation or 2 away.

In the event that mankind is wiped out to a handful of people and not enough for genetic diversity could the amount of people needed to repopulate the Earth be reduced by using Gene Editing and Modification?

Although several people survives in remote parts of the world only a few had good DNA, age and disease free to procreate.

With the help of a geneticists and a salvaged lab could DNA be modified to have your siblings baby but healthy?

As science progresses the plausibility of Adam and Eve giving rise to a whole world sounds more and more realistic to me. Can humans be so genetically perfect not to have defect for many generations?

What is the minimum human population necessary for a sustainable colony?

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    $\begingroup$ It is one thing to fix known genetic defects, replacing them with known "good" copy of DNA fragment. It is another to introduce random mutations just to create diversity. Which one are you asking about? $\endgroup$ – Alexander Mar 22 '18 at 22:00
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    $\begingroup$ "There will not be enough people for a gene pool to repopulate." The MVP for humans is less than 4200 people. If there aren't that many people, there's no hope of them running a DNA lab while struggling to survive. $\endgroup$ – RonJohn Mar 22 '18 at 22:01
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    $\begingroup$ If you are going to ask whether something can be done in such a vague manner, you should first ask yourself why it would not be possible. $\endgroup$ – Renan Mar 22 '18 at 22:10
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    $\begingroup$ "With no electricity DNA spoils" That's not how DNA works. $\endgroup$ – RonJohn Mar 23 '18 at 3:55
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    $\begingroup$ "It said able to conceive there could be more people." Twelve humans in their breeding years (which includes older men), and a lot of post-menopausal women. We keep telling us why your question is flawed, but you keep ignoring us. $\endgroup$ – RonJohn Mar 23 '18 at 10:15

Easier, More Effective Methods Available

Genetically modifying people to inbreed doesn't make much sense when there are better options on the table. The easiest we could do with today's technology is to freeze sperm and eggs so that you can artificially rejuvenate the gene pool periodically. On top of this, if the planet is smacked hard enough to kill off that many people basically the entire ecology of the planet is dead too so there really isn't any way for humans to survive or maintain a high level of technology anyways.

  • $\begingroup$ I have revised the question $\endgroup$ – Muze the good Troll. Apr 25 '18 at 21:21

Inbreeding is only a problem if there are genetic diseases in the DNA. If you remove all traces of genetic disease then inbreeding isn't a problem (until new mutations cause new ones anyway).

That said, they'll be blown back to the stone age so a scientist's time would be better spent building a better bunker or spacecraft than building incest resistant people.......

  • $\begingroup$ Genetics are tiny edits where extra people my not be possible. $\endgroup$ – Muze the good Troll. May 20 '18 at 4:04

The trouble with inbreeding is all about the fact that we have TWO copies of every gene; because we get one chromosome from each parent.

So; if you get a mutant allele that doesn't work from one parent, the chances are you won't even notice if you got a functional version from the other parent. This happens all the time.

When two people who are closely related have children, the chances of the child getting two bad copies of a gene increase very substantially, because both parents have a recent common ancestor who gave them their genes.

Also, the idea of 'genetic diseases' is not entirely correct. For any gene, there are thousands of alleles; each one might differ by only one nucleotide. Some are more or less functional but since the function of most proteins (proteins are encoded by genes) are very complex, each allele can be more functional in one situtaion and less functional in another

Consider the sickle cell gene; it makes a 'faulty hemoglobin protein' which aggregates at low oxygen tensions. But that same protein is protective against the malaria parasite (which lives inside red blood cells). So the same allele of hemoglobin is harmful (can't carry oxygen as well) but is protective against a very nasty disease for which there is no cure. Most alleles are like this; they have advantages and disadvantages.

  • $\begingroup$ I have revised the question $\endgroup$ – Muze the good Troll. Apr 25 '18 at 21:20

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