Types of Mutations

The mutation rate for most genes is 1:100,000 to 1:1,000,000. Thus, if an organism has 10,000 genes the chance that any of its gametes would contain a mutant gene is 1 - 10%. There are many recessive mutations that tend to remain hidden in the population until inbreeding (i.e., the mating of individuals more closely related than the average of the population to which they belong) occurs. Inbreeding allows these recessive genes to take on a homozygous condition and become expressed. Some of these genes are lethals, meaning that they will kill the offspring in either the prenatal or postnatal period prior to maturity.

Mutations occur through various events. I will discuss the most common events and those that would be more applicable to cockatiels.



Inversion involves two breaks to a single segment within the same chromosome and the broken segments reinserted into the same chromosome in an inverted position. A plausible explanation for inversion is entanglement of chromosome material during meiotic prophase and simultaneous breakage. See the figure below.

Chromosome Deletions