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I know this probably sounds rather hypothetical and not very feasible but I would very like an answer telling why it is possible or not possible and why.

With the advancement of crispr and other dna technologies, I have been wondering whether it is possible for us to use a virus, which would easily pass through the gaps of the placenta and infect the developing fetus to alter its genomic materials for the creation of designer babies. Since Zika can alter the genome of a baby to cause deformities, is something opposite also possible, like using a similar virus to develop favourable genes in a fetus.

Also, what are the chances of the virus actually purposely acting under orders of genetic engineering to intentionally deliver the genes through transduction?

Putting all ethical and moral issues aside is such a principle feasible and if no, why not?

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Zika doesn't alter the host genome at all.

Since Zika can alter the genome of a baby to cause deformities

Zika virus is incapable of altering the host genome. The exact mechanism by which Zika virus infection causes microcephaly is still unclear, but basically it depletes the neural stem cells at a point when the brain is developing, meaning brain development is more limited (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5516183/).

Some viruses do alter the host genome and are candidate technologies for gene therapy

Retroviruses are RNA viruses that copy their genetic material into DNA which is then integrated into a host genome. As such, and as you note, this can potentially be exploited to deliver new genetic material into an organism's genome. I'm not sure what you meant by transduction above, but the term is 'retroviral vector-mediated gene delivery'.

Retroviruses have been trialled for gene therapy for decades. See this sad report on a 2002 trial that apparently succeeded but had unexpected side effects here. However, CRISPR is probably an easier method to use.

You wouldn't attempt to modify a fetus

Some terminology here: a fetus is what an embryo grows into; it's getting bigger and more complex. And as illustrated by Zika-related microcephaly, any messing about with fetal development can have nasty side effects. There are also more cells to modify and you're likely to end up with a 'mosaic' where some cells are genetically different to others within the same organism. If you're attempting to modify the somatic cells of one organ, you might as well do it after the baby is born; if you're attempting to modify every cell in a human (including germ line cells) you'd do it to an egg or embryo.

This study describes a successful attempt to modify embryos using CRISPR. They saw only 1 mosaic in 58 embryos.

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First of all, disclaimer: We do not know the effects of every gene in the human genome. The human genome has only 1.2% of its genes that actually seem to be useful. However, the 98.8% of "junk" DNA may have uses that we don't know about. Also, many genes, such as sickle cell anemia, carry unknown benefits, such as offering resistance to malaria. Now, to answer your question...

Viruses

Viruses are probably some of the coolest things on the planet. They infect other organisms, which is a hard task to accomplish. According to Khan Academy they use two cycles.

  • The lytic cycle: The phage infects a bacterium, hijacks the bacterium to make lots of phages, and then kills the cell by making it explode (lyse).
  • The lysogenic cycle: The phage infects a bacterium and inserts its DNA into the bacterial chromosome, allowing the phage DNA (now called a prophage) to be copied and passed on along with the cell's own DNA.

Some viruses only use one type of cycle, the lytic cycle. However, you could use a virus with the lysogenic cycle to insert DNA into the target embryo, which could potentially accomplish your goal.

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