Postzygotic mutation

Mutagens often demonstrate mutational specificity, meaning they cause predictable changes in the DNA sequence.

However some mutations like DNA code change, epigenetic alterations and chromosomal abnormalities, can occur later in development.

[7] The loss of chromosome Y (LOY) in blood cells is the most common human postzygotic mutation.

[11] Smoking increases the risk of inducing LOY more than three times and has a dose-dependent effect on LOY-status.

While high-grade trisomy 21 mosaics, demonstrate similar features to full Down Syndrome, low-grade mosaics have a tendency to show milder features; however, the effects are quite variable depending on the distribution of the trisomic cells.

This type of mutation also involves cells outside of the reproductive group and thus is not transmitted to future descendants.

Depurination mutation results in one normal strand and one shortened strand after replication.
Mosaicism arises after the zygote has formed and a mutation occurs during development. The mutated cell line can be passed down to offspring if the germ cells are affected.