TOP 10 GENETIC MYTHS IN AVIan GENETICS by Linda S. Rubin All Rights Reserved Introduction pay attention to what is written on the in- Not surprisingly, and despite innumer- ternet, or passed on as good advice by the able benefits, aviculturists continue to find well meaning, to sometimes discover that it daunting to explore the principles that what is stated from “experts” may not be as explain heredity. Even the word, “genet- factual as hoped for. The following attempts ics” may cause some to inwardly cringe and to address some of the top ten myths that shudder. Yet, genetic principles are crucial are still perpetuated today in avian genetics to our understanding, because knowledge so that we can side-step these errors. of genetics can empower aviculturists with the ability to produce healthier strains of vi- Genetic Myth #1: Mutations are able breeding stock and future generations synonymous with hybrids. False! of robust species. When correctly bred, There is still much confusion around the breeding lines pass on such set qualities as differences between breeding color muta- increased egg production, higher fertility, tions within a species, and producing hybrid strong immune systems - and when prop- offspring between two different species. Linda S. Rubin erly applied - the ability to produce primary For clarity, the term “mutation” refers to Amazon parrot to a Lutino mutation Red- and rare color mutations to order. An un- changes in the outward color or pattern of lored Amazon parrot, would produce all derstanding of simple Mendelian rules and a bird. So, what are color mutations? Muta- Red-lored Amazon parrots. In other words, other modes of inheritance need not be tions may be caused by a variety of factors, all resulting offspring - whether nominant complicated, and many models, once un- but generally arise in aviculture as a sudden (wild colored) Red-lored Amazons, or Lu- derstood, are surprisingly simplistic. onset of a variation known as a spontaneous tino mutation Red-lored Amazons, would Although our first inclination is to ap- mutation which produces a new, anomalous all be the same species - 100% Red-lored ply genetic principles to outward color mu- color or pattern that differs from the nomi- Amazon parrots (Amazona autumnalis). tations and patterns in birds, the laws of nant (wild form) of the species. Some spon- Therefore, generally speaking, when ex- genetics equally pertain to all the traits in- taneous, partial mutations - if not fully de- amining a new color or pattern mutation, herited in a bird’s genotype. When applied veloped - may require a planned, selective we are looking at an example of a color mu- correctly, the laws of genetics allow us to breeding program requiring several genera- tation in the nominant wild species. We produce large, saleable baby birds raised by tions to achieve the full maturation of the are not looking at the offspring of dissim- fertile parental generations who success- final mutation. ilar species, but rather where both parents fully incubate, feed, and wean their own Viable mutations are able to reproduce are the same species. An example of a color babies, and also allows us to show the most because the genes - when inherited in the mutation would be a Blue Indian Ringneck exquisite bird to top perfected show stan- progeny - are either passed on as visuals (ho- Parakeet, bred from Indian Ringneck par- dards. In other words, the principles of he- mozygous), or carried as splits (heterozy- ents. An example of a hybrid would be off- redity affect every inherited trait - both visi- gous), depending upon the full genotype of spring from dissimilar species, e.g., one In- ble and invisible - in a bird’s genotype or full the parental generation. dian Ringneck Parakeet parent and one genetic makeup. Producing hybrids, on the other hand, Alexandrine Ringneck parent. Many of us learn avian genetics from requires mating a bird of one species to a Although color mutations are encour- our own hands-on work “in the field” (i.e., bird of a different species. For example, aged and sought out by many avicultur- the aviary), and from information gathered breeding Red-lored Amazon parrots to ists, most avicultural organizations frown and contained in our own studbooks, rather Green-cheeked Amazon parrots would re- upon the production of hybrids for an im- than through formal study. Our budding sult in offspring that are neither 100% ge- portant reason. Producing hybrids and knowledge and gradual absorption of facts netically Red-loreds (Amazona autumna- breeding their successive young will dilute over time contribute to the subtle and seem- lis), or 100% Green-cheeked Amazons ( the limited gene pool of stock available for ingly effortless process of learning through Amazona viridigenalis). Instead, the two the species involved. To continue to do so osmosis. Admirable. Except that even the different species would produce hybrid off- may affect the future availability of spe- most successful aviculturist may not possess spring that would not be recognized as ei- cies. Whereas, producing color mutations the text book knowledge to separate scien- ther species - autumnalis or viridigenalis. is simply changing the color and/or pattern tific fact from popular misinformation. We On the other hand, breeding a Red-lored 58 Volume XLII • Number 2 & 3 • 2013 of the species outwardly and in no way af- characteristic or trait. DNA in a gene can be the wild due to such factors as a more lim- fects their future establishment in captivity caused to mutate by two major occurrences. ited gene pool, the increased chance of sur- when bred responsibly. A mutation can be acquired due to envi- vival, and possibly an increase in genetic ronmental effects such as radiation or other drift. For example, this may be why we are Genetic Myth #2: Color mutations, agents, or when errors occur when a cell beginning to find more color mutations oc- compared to the nominant copies its DNA prior to the cell dividing. cur with the increase of producing some of species, are inherently weak. Mutations can be inherited randomly the larger Psittacine birds compared to de- from one or both parents. If a parent has cades ago. False! Mutations are a permanent change a mutation in its DNA, that mutation is Although established mutations can be in the DNA sequence of a gene affecting then passed on to its offspring. Mutations purchased and bred to reproduce in the avi- the genetic information of a hereditary occur more frequently in captivity than in ary, new mutations occur randomly and cannot be deliberately created, but rather, happen by chance. A common misconception is that color mutations, when compared to the nomi- nant (wild) species, are inherently weak. Al- though there are a few autosomal recessive mutations in aviculture that have had in- herent difficulties, it is not a given that new color and pattern mutations will be associ- ated with problem outcomes or lethal genes. One example of positive intervention occurred with the supposed original emer- gence of the (autosomal) Recessive Silver Cockatiel in Europe during the early 1960s, when it was first reported to have pro- duced chicks that were born blind. While first breeding cockatiels in the mid-1970s, the author became aware of Recessive Sil- vers imported from Europe, some few years later. These birds, however, did not have the inherent blindness or weakness of the ear- lier birds and were, in fact, quite healthy. It appears the lethal genes were either selec- tively bred out, or equally likely, as rumor had it, a new strain of Recessive Silvers were developed, one which did not carry any le- thal factors. Whenever another gene or allele becomes available, the one easiest to work with often finds favoritism. For example, in exhibition Budgerigars, once the Australian Domi- nant Grey color mutation became available, which appeared identical to the recessive Grey, interest waned in working with the English Recessive Grey that required a min- imum of two generations to produce visuals. Aviculturists naturally favored the Austra- lian Dominant Grey, which would produce visuals in half the nest in the first genera- tion. These Dominant Greys, carrying large AFA Watchbird 59 size, good head qualities, and other coveted show characteristics often found their way table 1 to the top of the show bench. It was not un- Sex-linked inheritance usual to find the (nominant wild) Normal Greens, Dominant Greys - and the cross – Cock Hen Progeny 1. Sex-linked Non-linked = 50% Non-linked/Sex-linked Grey-greens, to make up the top ten bench cock at many exhibition budgerigar shows. 50% Sex-linked hens There are instances of weakened ino (i.e., 2. Sex-linked Sex-linked = 50% Sex-linked cocks Lutino or Albino) mutations that have been 50% Sex-linked hens labeled as defective in some way, e.g., weak, 3. Non-linked Sex-linked = 50% Non-linked/Sex-linked inferior, “poor doers,” and who inherit a cocks multitude of problems from eyesight diffi- 50% Non-linked hens culties to immune compromised defenses. 4. Non-linked/Sex-linked Non-linked = 25% Non-linked/Sex-linked Although some birds may be affected ini- cocks tially in some species, aviculturists have 25% Non-linked cocks proven that line-breeding and affective out- 25% Sex-linked hens crossing can breed out problems initially ef- 25% Non-linked hens fecting a line of birds. 5. Non-linked/Sex-linked Sex-Linked = 25% Non-linked/Sex-linked In fact, there are quite a number of ro- cocks bust, healthy inos frequently seen at bird 25% Sex-linked cocks shows, including many winning top bench 25% Sex-linked hens ino mutations, and champion pedigreed 25% Non-linked hens inos who keep winning top awards, repro- ducing winning progeny.