Difference Between Allelic-Imbalance Copy Number Change And Allelic-Balance Copy Number Change

Question

[user1202664]

Consider two alleles, A and B at the same locus on homologous chromosomes.

• Allelic Balance: in one type of structural gain/loss, there is no resulting allelic imbalance; examples: AB ==> AABB (duplication), AB => -- (loss).

• Allelic Imbalance: in the other type of structural gain/loss, there is resulting allelic imbalance; examples: AB ==> AAB (duplication of A), AB => -B (deletion LOH), AB ==> BB (copy-neutral LOH).

First, is what I have described above correct?

Second, if it is correct, what is the biology underpinning these copy number aberration types? Are the mechanisms responsible for bringing about allelically-imbalanced CN change distinct from the mechanisms for bringing about allelically-balanced CN change? What are these mechanisms?

NB. I'm confining this to just copy number-related allelic imbalance.

Answer 1

[Sean Davis]

In my experience, it is unusual to have a copy number change that does not result in an allelic imbalance. The alternative, copy-number-neutral allelic imbalance is not that unusual, though.

[user1202664]

Less common than allelic-imbalance events, yes. But is that because there is a different mechanism at play, or is it just due to the lower probability of having two copy-number aberrations of the same type at the same locus on homologous chromosomes?