In a first in USA, scientists edit DNA of human embryos

A group of scientists at the Oregon Health & Science University edited the DNA of viable human embryos efficiently and apparently with few mistakes.

However, the experiment was just an exercise in science and the embryos were not allowed to develop for more than a few days and were never intended to be implanted into a womb.

The officials at Oregon Health & Science University confirmed on 27 July 2017 that the experiment was indeed conducted. They went on to state that results would be published in a journal soon.

The experiment is thought to be the first such work in the United States of America. Previously, experiments like this have been reported from China. However, how many embryos were created and edited in the experiments has not been revealed.

The biologists deem the step as a great potential to avoid many genetic diseases. However, they have also raised fears of "designer babies" if done for less lofty reasons, such as producing desirable traits.

How the experiment was conducted?

• The Oregon scientists reportedly used a technique called CRISPR-Cas9 genome editing technology, which allows specific sections of DNA to be altered or replaced.

• The technique is like using a molecular scissors to cut and paste DNA. It is much more precise than some types of gene therapy that cannot ensure that desired changes will take place exactly where and as intended.

• With gene editing, the so-called germline changes are permanent and would be passed down to any offspring.

About CRISPR

• Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) are segments of prokaryotic DNA containing short, repetitive base sequences.

• They play a key role in a bacterial defence system, and form the basis of a genome editing technology known as CRISPR/Cas9 that allows permanent modification of genes within organisms.

• In a palindromic repeat, the sequence of nucleotides is the same in both directions. Each repetition is followed by short segments of spacer DNA from previous exposures to foreign DNA.

• The CRISPR/Cas system is a prokaryotic immune system that confers resistance to foreign genetic elements such as those present within plasmids and phages that provides a form of acquired immunity.

• CRISPRs are found in approximately 40% of sequenced bacterial genomes and 90% of sequenced archaea.

• A simple version of the CRISPR/Cas system, CRISPR/Cas9, has been modified to edit genomes.

• By delivering the Cas9 nuclease complexed with a synthetic guide RNA into a cell, the cell's genome can be cut at a desired location, allowing existing genes to be removed and/or new ones added.