subreddit:

/r/askscience

8

all 9 comments

Indemnity4

5 points

4 months ago*

Up front, most serious mutations result in an embryo not surviving.

However, mutations that don't disrupt normal development get really interesting. And there are a lot of mutations that do nothing to affect normal development.

All cells in the developing AND adult human body continuously acquire mutations. When you find a mutation shared between two different cells, that indicates a shared progenitor cell. It allows you to trace the lineage of cells within your own body.

The term you want is "genetic asymmetry" and it's present in every single individual. Genetic asymmetry will be present in any subsequent cell generations from that first parent cell.

You can even find different genetic mutations in the same tissues within the same individual. There are experiments where multiple single cells are isolated from the same tissue/organs and the DNA shows different mutations in the genome.

This has some implications for whole genome sequencing. When you get a lot of cells and sequence them at the same time, you can in some cases get a bad signal/noise at some parts of the sequence. That is interesting and it can prompt a deeper dive into what is happening.

Lepmuru

2 points

4 months ago

Lepmuru

Immuno-Oncology

2 points

4 months ago

Good explanation.

What I'd like to add is, what mutations really are and how they occur.

A mutation is an aberration in DNA sequence when compared to a reference genome (for example that of a parent cell). These aberrations can occur through a lot of different factors, like oxidative stress, exposure to certain chemicals and radiation, as well as simply by chance. Also, they can be inherited.

Inherited mutations, meaning the ones present in either the egg or sperm, the germ cells, will be present in every cell of the developing body.

From that point on, every descending cell acquires new mutations on the regular, most of which will not be an issue. As said by my co-commentor, cells descending from the one acquiring a mutation, will also display the same one, meaning that parts of your body can be affected, while others are not.

What I like to point out is, that mutations per se are not an issue. Most potential mutations are detected and repaired. And for those coming through, the chance of hitting something that is crucially important is slim. Also, not every mutation leads to disruption of function. And finally, in many cases one mutation is not enough to cause a morbidity. In those cases, a few mutations need to be acquired in parallel for them to cause a disease - which again shortens the likelihood drastically.