Genetically Modified Humans?
It’s always exciting to be the first person to do something interesting. Just take a look at all the crazy stunts people attempt to get into the Guinness Book of World Records. Most Big Macs consumed in a lifetime…really?
Significant firsts are often celebrated, but this definitely did not occur last week when Chinese scientist He Jiankui claimed to have made the world’s first genome edited babies--twin girls named Lulu and Nana--who were born this month.
(Update: Researchers have since shown He missed his target, accidentally making the genes of one twin stronger than another and possibly leaving one still vulnerable to HIV. It's also possible He caused permanent, damaging mutations to the DNA of both twins.)
When He Jiankui presented his extraordinary work at the Second International Summit on Human Genome Editing in Hong Kong last month, he was unanimously criticized for his “unexpected and deeply disturbing claim.” I must add that there has been no independent confirmation that He has done what he’s said he’s done. His work also hasn’t been published in a peer reviewed scientific journal, either.
It’s clear, though, that his claim to have edited the genetic code of humans has provoked shock and outrage among scientists all over the world.
So what’s the science behind all of this? And what are the ethical concerns of editing the human genome?
Dolly, the first ever cloned sheep, is now stuffed and on display in the National Museum of Scotland in Edinburgh, Scotland. (Image credit: Wikipedia Commons.)
Genetic modification has a very long history. For thousands of years before scientists even knew our genetic information was stored in DNA, humans have tried to produce better animals and plants using selective breeding techniques.
Dogs are believed to be the first animal our ancestors artificially selected for breeding, and this technique has been also utilized with a variety of plants. However, selective breeding and artificial selection processes are somewhat random, and there’s little control over them.
Now, things are a bit different.
Artificially manipulating genetic material in a laboratory through genetic engineering has been an active field of research since the discovery of DNA in the 1950s. DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms.
Early researchers working on DNA used the term "gene" to mean the smallest unit of genetic information, a segment of DNA. Human DNA consists of about 3 billion bases, and more than 99% of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building an organism, similar to the way letters of the alphabet appear in a certain order to form words and sentences.
Genes are the basic physical and functional units of heredity. Every person has two copies of each gene, one inherited from each parent. There are more than 20,000 human genes. Most genes are the same in everyone, but a small number of genes (less than 1%) are slightly different between people.
Scientists keep track of genes by giving them unique names. Genes are also assigned symbols, which are short combinations of letters (and sometimes numbers) that represent an abbreviated version of the gene name. The human genome was completely sequenced in 2003. We know which gene is responsible for a disease and which gene controls your eye color.
Today, genome editing technology gives scientists the ability to change an organism's DNA. These technologies allow genetic material to be added, removed, or altered at particular locations in the genome.
Genetically modified organisms, known as GMOs, are plants or animals whose DNA has been modified in order to take on specific characteristics, like increased nutrients or a resistance against some disease. GMOs have been part of our food for the past 20 years. There are various commercially-grown GMOs like corn, canola, soybean and cotton. Even tobacco, rice, cranberries, raspberries and walnuts! Cattle, pigs, sheep, and dogs, among other animals, have also been safely genetically engineered.
Recently, a new gene-editing technology called CRISPR-Cas9 has been developed. It revolutionized gene editing. Researchers have learned how to target almost any genomic sequence by engineering an appropriate guide RNA. They couple it with an enzyme called Cas9, which can then cut both strands of a DNA sequence of interest at a specific site and replace it with a gene of interest.
Somatic genetic modification changes the genes in some of the cells of an existing person. These changes affect only certain tissues and are not passed from one generation to the next. These gene therapy techniques are approaching clinical practice, but only for a few conditions, and at a very high cost.
Germline genetic modification would change the genes in eggs, sperm, or early embryos. These changes would appear in every cell of the person who developed from that gamete or embryo and all of his/her children. It’s permanent. Germline cell and embryo genome editing are currently illegal in many countries.
This technology could cure genetic disorders, eradicate genes contributing to common human diseases and further research into disease. If the current claims of He Jiankui are true, this gene editing was done to make Lulu and Nana resistant to HIV infection. Scientists from all over the world are concerned not just because this technology isn’t considered safe for babies, but also because it opens the possibility of so-called designer babies.
This makes us think about the bigger question: Should we even be doing genetic modification at all?
(Dr. Yadav Pandit is an experimental nuclear physicist currently working at Allen Community College as a physical science instructor. He writes a column of general interest in science for the Register.)