Immortal Strand | DNA

The immortal DNA strand is a theory that suggests the asymmetric division of the DNA of adult stem cells through selective retention as opposed to random segregation during mitosis. The process also has the potential to retain a different outline of parental DNA strands per division.

The “immortal strand hypothesis” is an intriguing concept in the field of stem cell biology. Stem cells have the unique ability to undergo asymmetric cell division, wherein one daughter cell remains a stem cell (self-renewal) while the other daughter cell differentiates into a specific cell type.

The immortal strand hypothesis suggests that when a stem cell divides, it selectively retains the older, “original” or “immortal” strands of DNA, and passes the newly synthesized DNA strands to the differentiating daughter cell. The proposed advantage of this mechanism is that it would minimize the number of mutations accumulated in the stem cell pool, as DNA replication is a primary source of mutations. By retaining the older, “immortal” DNA strands, stem cells might protect their genome from replication-induced errors over time.

This hypothesis is based on the following ideas:

1. DNA Semiconservative Replication: When DNA replicates, each of the two daughter molecules will have one old (parental) strand and one new strand.
2. Protection from Mutations: Since errors can occur during DNA replication, by consistently segregating the older, presumably less mutated, DNA strand to the stem cell during cell division, the stem cell might limit the accumulation of mutations in its genome.
3. Observations in Certain Cells: Some experiments, particularly in intestinal stem cells, have provided evidence supporting the immortal strand hypothesis. These studies have shown preferential segregation of older DNA strands to stem cells during division.

However, the validity and universality of the immortal strand hypothesis are still debated:

1. 1. Contrary Evidence: Many studies, especially with more modern lineage tracing and DNA labeling techniques, have shown random segregation of old and new DNA strands in stem cell divisions, contradicting the immortal strand hypothesis.
   2. Not Universal: Even if the hypothesis holds true in specific cell types or under certain conditions, it might not be a universal feature of all stem cells.
   3. Alternative Mechanisms: Some scientists believe that stem cells have other methods for safeguarding their genome, such as more efficient DNA repair mechanisms.

While the immortal strand hypothesis presents a fascinating mechanism by which stem cells might preserve their genomic integrity, the concept remains controversial and requires further investigation.The Immortal Strand theory was first proposed by researcher John Cairns in 1975. To learn more about DNA and genetic testing contact us.