Submitted by soygang t3_xy2vlm in askscience
I'm wondering, how common any type of mutation however small is in homo sapiens. Do most people just have a combination of their parents genes, or do most people have some sort of mutation in some aspect of their genes? Is there any rough percentage ?
Everyone has some mutations in their genes. You have roughly 3 billion base pairs of DNA in your genome and the chance of a random mutation is high enough that it’s likely every conception involves at least one base pair substitution, segment snip, crossover, or flipped section.
Most mutations are not viable or not important - some of the genome is designed with redundant coding so that if there’s a base pair substitution, the same protein is encoded.
Thank you
>for example about 30% of autism cases are caused by de novo mutations
The linked paper appears to say that 30% of de novo mutations in people with ASD contribute to autism, not that 30% of instances of ASD are caused by de novo mutations. In my opinion, the claim they make in the abstract is not the same as the one they make in the paper itself (see page 219, the fourth page of the article, for the 30% figure in context).
Hmm, I re-read that section and I can't quite figure out what they're trying to say. You're right that it seems different from what they say in the abstract. I'll edit my original comment.
The last I heard (source) the current thinking was that simple repeat expansion was the source of most de novo mutations, leading to phenotypic changes and symptom severity. This isn't really my field so there might have been a more recent update, but I spend enough time dealing with structural changes to the genome that I read this one when it came out.
Repeat expansion doesn't really behave like a classical mutation, and is more a product of an increased likelihood of specific types of error in DNA replication and repair.
yeah I was gonna say, I think the exact causes of ASD and autism in general are pretty controversial and somewhat unsettled, particularly the exact way genetics plays a role, and which genes are most likely to be responsible, so unless there’s been some very recent major breakthrough, “30% of ASD cases are caused by de novo mutations” seems a really bold claim, considering that would make de novo mutations one of the most significant contributing causes by far, and at least last I heard, the exact genetic causes of autism were not that settled (and heritable genes were more often thought to play a large role in at least certain types of cases). The former, more conservative claim seems a lot easier to swallow.
A very good example of de novo Mutation having a direct and pathogenic effect (while still viable) is de novo Mutation on the CTNNB1 gene.
And a month ago it has been confirmed to be an actual diagnosis of a syndrome
-Metacelsus- t1_irf45q3 wrote
There are typically 44 to 82 mutations in each person's genome that are not found in their parents. These are called de novo mutations (meaning "new" in Latin). The number is higher if the father is older, since mutations slowly accumulate as spermatogonial stem cells divide over time.
Source: https://genomebiology.biomedcentral.com/articles/10.1186/s13059-016-1110-1
Most of these mutations have no biological effect, but some can cause health issues when important genes are mutated (for example some of these mutations can cause autism). For context, a typical human genome has about 4-5 million mutations relative to the reference genome (this is higher in individuals of African descent because humanity originated in Africa so there is more genetic diversity there). The haploid human genome is 3.1 billion bases long.