The fusion of two sisters into a single woman suggests that human identity is not in our DNA

🌈 Abstract

The article discusses the idea that human identity is not defined by DNA, but rather by the cells that make up the body. It presents the case of Karen Keegan, a woman who has two different DNA sequences in her cells, and argues that this shows that genes do not determine a person's uniqueness. The article also explores the role of cells in embryonic development and the concept of "gastruloids" - structures that partially imitate the human embryo and demonstrate the ability of cells to self-organize and communicate.

🙋 Q&A

[01] The fusion of two sisters into a single woman

1. What is the example used to illustrate that human identity is not defined by DNA? The article cites the case of Karen Keegan, a woman who has two different DNA sequences in her cells, as evidence that genes do not define a person's identity.

2. What happened to Karen Keegan when she was 52 years old? When Karen Keegan was 52 years old, she suffered from very serious kidney failure, but was able to receive a kidney donation from one of her three children.

3. What was the surprising result of the genetic tests done on Karen Keegan's children? The genetic tests showed that two of Karen Keegan's children were not actually her biological children, despite the fact that she had given birth to them. This was because Karen Keegan had two different DNA sequences in her cells.

[02] The selfish gene and the altruistic cell

1. What is the main idea of Richard Dawkins' book "The Selfish Gene"? According to the article, in "The Selfish Gene", Dawkins defended the idea that the DNA molecule uses the human being as a "mere envelope" in order to be transmitted to the next generation and become immortal.

2. How does Alfonso Martínez Arias' view differ from Dawkins' "selfish gene" perspective? Martínez Arias proposes a "much more romantic alternative" to Dawkins' "selfish gene" perspective, arguing that the "organism is the work of cells" and that "genes merely provide materials for their work". He suggests the idea of the "altruistic cell" instead of the "selfish gene".

[03] Cells as the true architects of life

1. What is Martínez Arias' view on the role of DNA in an individual's development? Martínez Arias argues that the DNA sequence of an individual is not an instruction manual or construction plan for their body, but rather a "box of tools and materials" for the "true architect of life": the cell.

2. What examples does the article provide to illustrate Martínez Arias' view that cells, not genes, control an organism's development? The article mentions that there is nothing in the DNA molecule that explains why the heart is located on the left, why there are five fingers on the hand, or why twin brothers have different fingerprints. Martínez Arias argues that it is the cells, not the genes, that "control time and space" and know where exactly a person's body parts should be.

[04] The importance of gastrulation in embryonic development

1. What is the significance of the gastrulation phase in embryonic development, according to Martínez Arias? Martínez Arias cites the phrase "it is not birth, marriage, or death, but gastrulation which is truly the most important time in your life" from his colleague Lewis Wolpert. He compares the gastrulation phase to a "cellular dance with a perfect choreography" that is crucial in the early stages of embryonic development.

2. How did Martínez Arias' team overcome the difficulties in observing the gastrulation process? The article states that Martínez Arias' team in Cambridge used a chemical cocktail to induce embryonic stem cells to form a three-dimensional structure similar to the result of gastrulation, called "gastruloids". This allowed them to observe, for the first time in history, something very similar to what happens during gastrulation in a mother's womb.

[05] Cells as the masters of construction

1. What do the "gastruloids" created by Martínez Arias' team demonstrate about the role of cells? According to the article, the gastruloids "unequivocally show that cells are the masters of construction, and that there is no blueprint in the genome to direct what they do." They demonstrate the cells' ability to self-organize, communicate with each other, and occupy their proper place in the structure.

2. What did Susanne van den Brink's discovery about the number of cells required for gastruloid formation reveal? Van den Brink discovered that gastruloids were only formed if a specific number of cells were used: about 400. This suggests that "cells know how to count" and that the dance of gastrulation will not begin without the proper number of cells present.