I am looking through a genomics database to see whether patients who have intellectual disability have deletion of only a specific gene of interest and no other mutations (e.g. deletions or copy number variations of other genes).

I have seen that some patients have deletion of the entire gene whereas other patients have deletion of only part of the coding region of the gene. However, even if part of the gene is deleted, patients have intellectual disability and other abnormalities.

I was wondering, in general, is it more serious for a person to have a deletion of an entire gene in contrast to having part of the gene deleted? Can having part of the coding region of a gene deleted be just as serious as having the entire gene deleted?


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    $\begingroup$ Highly gene dependent I suspect - delete an important motif in one gene then yes, delete one repeat in a highly repeat rich gene (e.g. Ankyrin repeats) and it might not be. $\endgroup$
    – bob1
    Commented Dec 17, 2021 at 9:46
  • 2
    $\begingroup$ I strongly agree with bob1, a particularly clear example is that some partial deletions will result in a dominant negative allele — these will have a stronger effect than a complete deletion. ——— Consequently, this is only answerable for specific deletions of specific loci. As written this isn't a question with a useful answer, so I've voted to close. $\endgroup$
    – tyersome
    Commented Dec 17, 2021 at 18:11

1 Answer 1


The answer depends as @bob1 says on the gene and the mutation probably.

For a simple analogy, think of a gene like a chainsaw or other piece of machinery.

To break it down a little:

Full gene deletion

We expect a full gene deletion to be associated with a loss of function. This is very bad if the gene is essential to life

If you lose your chainsaw, you can't cut anything, which is bad if you need to cut things e.g. for your job.

Partial gene deletions

Are more ambiguous. They might cause:

  • Full loss of function of the gene (equally bad to full deletion).
  • A crucial piece of your chainsaw is broken, so you can't start it.
  • Partial loss of function of the gene ("hypomorphs", less bad than full deletion).
  • There's something wrong the chain on the chainsaw, so it's slower than usual, but you can still cut some wood.
  • Gain of function of the gene (could be better or worse than full deletion!)
  • There is something wrong with the gas tank, and the chainsaw might explode and hurt you!

Gain of function is the most interesting but probably the rarest. Here is one example, where a partial deletion of the tumor suppressor gene p53 switches its function so it turns into an oncogene (a tumor promoter), effectively switching its function from protecting against cancer to making cancer more likely.

Here is a powerpoint from a class that goes over gain-of-function and loss-of-function in a little more detail.


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